Windows 8 offers many advantages compared to Windows XP, Windows Vista and even Windows 7. However, to take full advantage of all the new features in Windows 8, the hardware you run it on needs to be equipped with specific hardware.
The list below details the minimum hardware requirements for Windows 8-powered desktops, notebooks and tablets in detail:
Minimum specifications
Processor
Central Processing UnitBy now, you've probably heard of Windows 8 and Windows RT. Windows 8 is the familiar x86-based Operating System you've come to love and live with in the past years. Windows RT is a new breed of Windows, specifically designed to run on ARM-based processors.
At first glance, Windows 8 minimum requirements are equal to these of Windows 7. When you look closer, though, Windows 8 demands certain processor-specific technologies. First of all, the processor needs to support the Never Execute bit (NX-bit). It also requires SSE2.
NX is the limiting factor here. named Execute Disable in the world of Intel and is available in its processors since the 64bit-capable 90nm Prescott-based Pentium 4 processors (February 2004). The technology, dubbed Enhanced Virus Protection (EVP by AMD is available since the Opteron (April 2003) and Athlon64 (September 2003).
Coincidentally, both Intel and AMD introduced NX in processors at the same time as their 64bit capabilities in mainstream processors. With the exception of some netbooks, all prospective Windows 8 machines are able to run the 64bit versions of Windows 8.
RAM
Random Access MemoryWindows 8 requires a minimum of 1GB of RAM. This requirement is equal to Windows 7, but, like back in the early days of Windows 7, when you want a Windows 8 machine to run smoothly when you use demanding programs, I recommend 2GB RAM.
When you're running more demanding programs, even on rigs with 2 GB RAM, you're likely to run into a performance bottleneck. When Windows needs to allocate more RAM than is physically available, it will use the page file on the hard disk. Since disk storage is slower than RAM, this significantly hits performance. Adding RAM solves this problem.
Also, ReadyBoost, a feature that has been around since Windows Vista, can be used. Instead of using the page file on disk to expand RAM, first a file on a flash drive will be used. Flash drives are most commonly faster than disk storage. When using USB media, make sure it's at least 256MB in size, USB 2.0 compatible and plugged into an USB 2.0 socket.
Display
DisplayWindows 8 is primarily designed for wide screens. Many of the New User Interface elements work particularly well on 16:9 aspect ratio and 16:10 aspect ratio screens. You can install Windows 8 on machines with screens with 1024 x 768 resolutions. These machines will run Windows 8 and will display Windows 8 Apps.
However, it's a better idea to install Windows 8 on machines with screens with 1366 x 768 resolutions (and higher). When the screen offers at least 1366 x 768 pixels, you can use Windows Snap. With Windows Snap, apps (and the desktop) can be snapped to the side of the screen, allowing multi-tasking between Windows 8 apps and between Windows 8 apps and desktop applications.
Many tablets, that seem prime candidates for Windows 8 from a processor and RAM point of view, are unable to offer Windows Snap, due to their 1024 x 768 and 1280 x 800 resolutions and might offer a reduced Windows 8 experience.
Note:
Windows Snap can be enabled on lower resolutions using the Registry information here.
Video Card
Video CardWhile you might think you can finally reuse your beloved PCI-based S3 Trio64 video card, because it will be able to output a 1024 x 768 resolution, the video card will need to be compatible with DirectX 9.0 or higher. It will need to be Direct3D 9-capable and its manufacturer will have to support its card with a WDDM 1.0+ driver.
Many Nvidia cards are Direct3D 9-capable since the 6xxx series in 2004. ATI's DirectX 9.0 technology was introduced in 2002, released as Radeon 9500–9800, X300–X600, and X1050. As a rule of thumb, you can use your graphic card when it's newer than 2004. Integrated graphics, like the Intel GMA 950, 3000, x3000, 3100 and 500 families, supported Direct3D-9 from 2006.
Note: When you plan to multi-boot or downgrade the machine to Windows 7, the aforementioned video cards will only make the system 'Compatible with Windows 7' and you will need to live without Aero Glass and Flip 3D on Windows 7 (features removed from Windows 8). To enable Aero Glass and Flip 3D, you'll need a DirectX 10+-capable video card with WDDM 1.1+ drivers.
Everything higher spec'd will not benefit you in a significant way when you plan to merely use the Windows 8 interface. When you plan to play 3D games, however, a more sophisticated video card will make a good Christmas gift.
Hard Disk Space
Hard DiskMicrosoft recommends 16GB of free hard disk space for 32bit (x86) installations of Windows 8. For 64bit (x64) installations of Windows 8, a minimum of 20GB is specified. When you upgrade to Windows 8 from a previous version of Windows, you'll need 7768 MB of free space on the system disk (the disk where the Windows folder lives).
However, depriving Windows 8 from disk space from the get-go, might become a sour decision after a while. It's fine when you limit the disk space for test machines, but when you're a few months down the line, you'll no longer be able to download and install updates, due to low disk space.
Also, by default, Windows will create a hibernation file (when the system supports low power states and a page file. Providing a 20GB disk to Windows on a machine with 8GB RAM, will cause problems.
22 Jan 2013
PowerShell, LDIFDE, CSVDE and Protection from Accidental Deletion
When you build test environments regularly, at some point you'll want to fill your Active Directory quickly. If, for instance, you have a data set with Organizational Units (OUs), user accounts and groups, you'll want to quickly import this data. If, on the other hand, in your business you're allowed to use the user information from a production Active Directory environment in your test environment, you might even opt to export and import this information.
Besides restoring backups from Domain Controllers to the test environment, Microsoft offers three tools to import exported data:
- Import-CSV & New-ADOrganizationalUnit
- Csvde.exe
- Ldifde.exe
From the surface, these three tools seem to enable you to achieve the same goal, but they don't. The end result after importing and exporting data is not the same between these three tools.
When you use the New-ADOrganizationalUnit PowerShell Cmdlet (together with the Import-CSV Cmdlet in this case) in a script, unless you specify otherwise, the created Organizational Units will be protected from accidental deletion.
When you use ldifde.exe or csvde.exe tool to (export and) import Organizational Units (OUs), these OUs will be created without protection from accidental deletion.
Protection from accidental deletion looks like a simple checkmark in the properties of an Active Directory object, but it's not. Underlying is a set of ACLs that prevent anyone from deleting the object. But since PowerShell has the logic inside for Protection from accidental deletion, to fix the newly created Organizational Units, use the following PowerShell one-liner:
Besides restoring backups from Domain Controllers to the test environment, Microsoft offers three tools to import exported data:
- Import-CSV & New-ADOrganizationalUnit
- Csvde.exe
- Ldifde.exe
From the surface, these three tools seem to enable you to achieve the same goal, but they don't. The end result after importing and exporting data is not the same between these three tools.
When you use the New-ADOrganizationalUnit PowerShell Cmdlet (together with the Import-CSV Cmdlet in this case) in a script, unless you specify otherwise, the created Organizational Units will be protected from accidental deletion.
When you use ldifde.exe or csvde.exe tool to (export and) import Organizational Units (OUs), these OUs will be created without protection from accidental deletion.
Protection from accidental deletion looks like a simple checkmark in the properties of an Active Directory object, but it's not. Underlying is a set of ACLs that prevent anyone from deleting the object. But since PowerShell has the logic inside for Protection from accidental deletion, to fix the newly created Organizational Units, use the following PowerShell one-liner:
- Get-ADOrganizationalUnit -filter {name -like "*"} -Properties ProtectedFromAccidentalDeletion | where {$_.ProtectedFromAccidentalDeletion -eq $false} | Set-ADOrganizationalUnit -ProtectedFromAccidentalDeletion $true
21 Jan 2013
8 Awesome Questions Answered By Windows 8
Microsoft does such a great job of having a full solution for enterprises. I've heard some people question the costs of the licenses in contrast to other vendors or open source solutions, but there is no open source solution or vendor that can cover everything that Microsoft products can.
It can be really easy to love Microsoft if you're an IT professional that works on their products. Easy to use GUIs, free training and documentation, and market share that can find you a job in any location.
Still, there are a few nagging questions that can get you wondering, "Is Microsoft ever going to get this right?" Sometimes it seems like Microsoft just messed up a feature, or they just don't understand what we want to do.
So now, in honor of Windows 8, here are my top 8 questions that Windows 8 has an answer to.
Question 1: Why can't I have Hyper-V on my laptop? What ever happened to Virtual PC?
Client Hyper-V, full featured virtualization software, is finally coming to workstations in Windows 8! Client Hyper-V is installed as a feature, so you don't have to buy it separately. It includes all of the features that you expect from your virtualization software: virtual networking, shared drives, and most importantly, snapshots.
You can also use the advanced features of Hyper-V on your installation of Windows 8 desktop. For example, Client Hyper-V allows you to automate your virtual environment using PowerShell, and if you've got a multipoint touch-enabled device that you're running client Hyper-V on, you can also use your touch screen on your VMs.
Question 2: When will I be able to use my own tablet as my work computer?
One of the key devices Windows 8 has been aimed at is the tablet. It's touch ready, and ready for you to take it with you. It has also been designed to help IT departments manage the huge rush of personal devices into the workplace. The consumerization of IT is making end-users the champions of new technology devices, a role that was previously held by the IT staff.
Determining whether or not a computer is yours, or one you're just using temporarily, is handled by the Windows 8 feature "User Device Affinity." User device affinity uses usage percentage, amount of time logged in, and number of times logged in to determine if the computer belongs to you enough to call it "your computer." If it is the computer that you usually use, regardless of who actually owns the computer, your Windows 8 tablet will identify it as a primary device. A new feature in System Center Configuration Manager 2012 allows administrators to target those primary devices for software installations, whether they are company owned or employee owned.
Question 3: How can my Blu-Ray player and TV "boot up" in under a second, but my computer still takes a full minute?
Windows 8 is faster overall, and in many areas. One area in particular where it is dramatically improved is in its startup time. Using partial hibernation, which stores a set of system files and RAM on the hard drive (but not all of the running programs and RAM that would be used in a full hibernation), Windows 8 systems have been booting up from a cold start in under 10 seconds. Solid State Drives report it even faster, almost instantly.
Question 4: Why can't I take my programs with me to whatever computer I'm at?
Brand new with Windows 8 is Windows To Go. Windows To Go allows IT staff to load a full version of Windows 8 on a USB drive, including the operating system, personal data, and installed programs!
There are some differences in using Windows To Go: You're presented with a pre-boot password prompt; If you remove the USB device, the computer freezes in place until the USB device is plugged back in; and booting into your Windows To Go disables hard drives on the physical computer to help prevent your data from being compromised.
Question 5: Where is the factory reset button?
If you've wished that your HP or Dell PC came with a factory reset button like your home wireless router does, you'll be happy to see that Windows 8 provides two features that provide functionality for doing just that: Reset and Refresh. Both are now accessible from the Control Panel metro app, and both will fix problems with your PC. Reset takes it back to the day it was purchased: all apps are gone and all user data is gone. Refresh performs a full reinstall of Windows, but saves your user data, most of your preferences, and saves your installed metro apps.
Question 6: Why does malware start on a PC before anti-malware does?
In Windows 8, there looks to be some great strides taken to prevent malware that starts early in the boot process from being able to mess up your system. Trusted Boot in Windows 8 digitally signs your bootup environment, validating the entire process. The loading of anti-malware software is one of the earliest actions performed by Windows 8, so it is running before malware even has a chance to start.
Question 7: How can the world's largest software company not have an app store?
Microsoft finally reveals an App store on their desktop operating system with Windows 8. Microsoft has already had an app marketplace that is still used with Windows Phone (via Zune software), but you can now have apps purchased, stored, and delivered directly to your desktops, laptops, and tablets running Windows 8.
Question 8: Why in the world can I not mount an ISO on a Windows machine?
Now, after many years that I have been asking this question, you can finally mount ISOs in Windows 8 as part of the operating system. There are no third party utilities required. You can also mount VHDs (Virtual Hard Disks) natively in Windows 8.
ISOs show up as a new CD or DVD drive, while VHD shows up as a new hard drive. You can access either ISOs or VHDs by either double-clicking them, right clicking them and selecting "mount," or by selecting the "mount" from the ribbon in Windows Explorer.
It can be really easy to love Microsoft if you're an IT professional that works on their products. Easy to use GUIs, free training and documentation, and market share that can find you a job in any location.
Still, there are a few nagging questions that can get you wondering, "Is Microsoft ever going to get this right?" Sometimes it seems like Microsoft just messed up a feature, or they just don't understand what we want to do.
So now, in honor of Windows 8, here are my top 8 questions that Windows 8 has an answer to.
Question 1: Why can't I have Hyper-V on my laptop? What ever happened to Virtual PC?
Client Hyper-V, full featured virtualization software, is finally coming to workstations in Windows 8! Client Hyper-V is installed as a feature, so you don't have to buy it separately. It includes all of the features that you expect from your virtualization software: virtual networking, shared drives, and most importantly, snapshots.
You can also use the advanced features of Hyper-V on your installation of Windows 8 desktop. For example, Client Hyper-V allows you to automate your virtual environment using PowerShell, and if you've got a multipoint touch-enabled device that you're running client Hyper-V on, you can also use your touch screen on your VMs.
Question 2: When will I be able to use my own tablet as my work computer?
One of the key devices Windows 8 has been aimed at is the tablet. It's touch ready, and ready for you to take it with you. It has also been designed to help IT departments manage the huge rush of personal devices into the workplace. The consumerization of IT is making end-users the champions of new technology devices, a role that was previously held by the IT staff.
Determining whether or not a computer is yours, or one you're just using temporarily, is handled by the Windows 8 feature "User Device Affinity." User device affinity uses usage percentage, amount of time logged in, and number of times logged in to determine if the computer belongs to you enough to call it "your computer." If it is the computer that you usually use, regardless of who actually owns the computer, your Windows 8 tablet will identify it as a primary device. A new feature in System Center Configuration Manager 2012 allows administrators to target those primary devices for software installations, whether they are company owned or employee owned.
Question 3: How can my Blu-Ray player and TV "boot up" in under a second, but my computer still takes a full minute?
Windows 8 is faster overall, and in many areas. One area in particular where it is dramatically improved is in its startup time. Using partial hibernation, which stores a set of system files and RAM on the hard drive (but not all of the running programs and RAM that would be used in a full hibernation), Windows 8 systems have been booting up from a cold start in under 10 seconds. Solid State Drives report it even faster, almost instantly.
Question 4: Why can't I take my programs with me to whatever computer I'm at?
Brand new with Windows 8 is Windows To Go. Windows To Go allows IT staff to load a full version of Windows 8 on a USB drive, including the operating system, personal data, and installed programs!
There are some differences in using Windows To Go: You're presented with a pre-boot password prompt; If you remove the USB device, the computer freezes in place until the USB device is plugged back in; and booting into your Windows To Go disables hard drives on the physical computer to help prevent your data from being compromised.
Question 5: Where is the factory reset button?
If you've wished that your HP or Dell PC came with a factory reset button like your home wireless router does, you'll be happy to see that Windows 8 provides two features that provide functionality for doing just that: Reset and Refresh. Both are now accessible from the Control Panel metro app, and both will fix problems with your PC. Reset takes it back to the day it was purchased: all apps are gone and all user data is gone. Refresh performs a full reinstall of Windows, but saves your user data, most of your preferences, and saves your installed metro apps.
Question 6: Why does malware start on a PC before anti-malware does?
In Windows 8, there looks to be some great strides taken to prevent malware that starts early in the boot process from being able to mess up your system. Trusted Boot in Windows 8 digitally signs your bootup environment, validating the entire process. The loading of anti-malware software is one of the earliest actions performed by Windows 8, so it is running before malware even has a chance to start.
Question 7: How can the world's largest software company not have an app store?
Microsoft finally reveals an App store on their desktop operating system with Windows 8. Microsoft has already had an app marketplace that is still used with Windows Phone (via Zune software), but you can now have apps purchased, stored, and delivered directly to your desktops, laptops, and tablets running Windows 8.
Question 8: Why in the world can I not mount an ISO on a Windows machine?
Now, after many years that I have been asking this question, you can finally mount ISOs in Windows 8 as part of the operating system. There are no third party utilities required. You can also mount VHDs (Virtual Hard Disks) natively in Windows 8.
ISOs show up as a new CD or DVD drive, while VHD shows up as a new hard drive. You can access either ISOs or VHDs by either double-clicking them, right clicking them and selecting "mount," or by selecting the "mount" from the ribbon in Windows Explorer.
20 Jan 2013
Microsoft Hyper-V Server 2012 Release Candidate Now Available
If you aren't familiar with Hyper-V Server, you aren't alone. It's quite natural to assume that, like "freemium" software, the free version of Microsoft's server virtualization solution has a cut-down feature set or is otherwise lobotomized compared to the full Windows Server Hyper-V role. You'd be mistaken. In both Windows Server 2008 R2 and Windows Server 2012, Hyper-V Server boasts the same features. What's the difference between the two, then? The first is that Hyper-V Server runs with a simple command line interface rather than a full parent partition on the virtualization host server. This lack of an interface is rarely a problem because you really shouldn't be managing a host server at its console anyway; you should be managing it remotely. And Hyper-V Server is remotely managed exactly the way you manage the full Hyper-V role, by using Hyper-V Manager in the Remote Server Administration Toolkit (RSAT) or System Center Virtual Machine Manager.
The second difference is in licensing. Unlike the full version, Hyper-V Server provides for no operating system environments (OSEs) to automatically license those Windows VMs on the host. Because of the way Microsoft virtualization licensing is designed, it's more advantageous for most customers to purchase Windows Server Datacenter and get unlimited OSEs than use Hyper-V Server and purchase licenses separately. There are, however, several scenarios where Hyper-V Server is a perfect fit and you can reduce your operating costs by using it. First, let's review a few of the highest-profile features in Windows Server 2012 Hyper-V.
Hyper-V 2012 Features
Last year, my colleague Mike Otey provided an overview of the wide range of significant features in Windows Server 2012 (then Windows Server 8) Hyper-V. To me, the feature with the broadest appeal to the widest array of environments is shared nothing (SNO) Live Migration. This is the ability to migrate a live VM from one Hyper-V host to another without the requirement of storing the VM's virtual disk files on an expensive storage device that is shared between the Hyper-V hosts. For example, you can migrate VMs between two standalone Hyper-V hosts that contain only built-in, direct attached storage. This dramatically lowers the cost barrier to implementing virtualization. If you add another new capability, that of hosting Hyper-V virtual disks on SMB file server shares, a whole new range of virtualization infrastructure possibilities open up. Add the easy-to-implement disaster recovery capabilities of Hyper-V Replica, and production-worthy virtualization is now available, at low cost, to companies of all sizes.
Once a nagging constraint, the scalability limits reached by Windows Server 2012 Hyper-V (and thus Hyper-V Server 2012) are such that I think no one simply ever needs to think about them again. Since Mike's article describing the Developer Preview, Microsoft has doubled many of the product's limits on top of the original 2 to 8 times improvement over R2's Hyper-V (Figure 1)! Jeff said at the time, "We can believe this product scales much higher – we just haven't had the time to test the upper limits."
All of these features are available in the free Hyper-V Server 2012.
Microsoft positions Hyper-V Server, regardless of version, mostly for use cases involving licensing. One scenario involves running Linux or other non-Windows VMs on Windows Server hosts. These VMs don't require Windows OSE licenses, so why pay for a copy of Windows Server Enterprise or Datacenter editions and their associated licenses when you can host them on Hyper-V Server? A second scenario is for the VDI (virtual desktop infrastructure) scenario. In this scenario, the VMs on the Hyper-V host are running a Windows client, not a Windows Server, so the OSE licenses included with Windows Server Hyper-V are wasted. A similar scenario is of hosting Windows OSes earlier than Windows Server 2008, such as 2003 or 2003 R2.
The last use case is for the "little to no IT" small business scenario. In this case, a Hyper-V host is situated at a small business where some employees are somewhat technical, but not up to the task of virtualization host server management. The bottom line is that you don't want them to logon to the parent partition and inadvertently do anything to harm the host. With a simple command line interface, there's nothing to tweak or otherwise poke around with.
How does Hyper-V Server 2012 compare to VMware's free version of ESXi 5.0, its vSphere Hypervisor 5? vSphere Hypervisor is limited to 4 vCPUs per VM, while Hyper-V Server supports up to 64. Host RAM is limited to 32 GB, while Hyper-V Server supports up to 4 TB. vSphere Hypervisor 5 also contains no VM migration (vMotion), storage migration (Storage vMotion), high availability, extensible switch or VM replication features. It can only be managed by connecting directly to the host with the vSphere client, whereas Hyper-V Server supports both Hyper-V Manager and System Center Virtual Machine Manager remote management.
The second difference is in licensing. Unlike the full version, Hyper-V Server provides for no operating system environments (OSEs) to automatically license those Windows VMs on the host. Because of the way Microsoft virtualization licensing is designed, it's more advantageous for most customers to purchase Windows Server Datacenter and get unlimited OSEs than use Hyper-V Server and purchase licenses separately. There are, however, several scenarios where Hyper-V Server is a perfect fit and you can reduce your operating costs by using it. First, let's review a few of the highest-profile features in Windows Server 2012 Hyper-V.
Hyper-V 2012 Features
Last year, my colleague Mike Otey provided an overview of the wide range of significant features in Windows Server 2012 (then Windows Server 8) Hyper-V. To me, the feature with the broadest appeal to the widest array of environments is shared nothing (SNO) Live Migration. This is the ability to migrate a live VM from one Hyper-V host to another without the requirement of storing the VM's virtual disk files on an expensive storage device that is shared between the Hyper-V hosts. For example, you can migrate VMs between two standalone Hyper-V hosts that contain only built-in, direct attached storage. This dramatically lowers the cost barrier to implementing virtualization. If you add another new capability, that of hosting Hyper-V virtual disks on SMB file server shares, a whole new range of virtualization infrastructure possibilities open up. Add the easy-to-implement disaster recovery capabilities of Hyper-V Replica, and production-worthy virtualization is now available, at low cost, to companies of all sizes.
Once a nagging constraint, the scalability limits reached by Windows Server 2012 Hyper-V (and thus Hyper-V Server 2012) are such that I think no one simply ever needs to think about them again. Since Mike's article describing the Developer Preview, Microsoft has doubled many of the product's limits on top of the original 2 to 8 times improvement over R2's Hyper-V (Figure 1)! Jeff said at the time, "We can believe this product scales much higher – we just haven't had the time to test the upper limits."
All of these features are available in the free Hyper-V Server 2012.
Microsoft positions Hyper-V Server, regardless of version, mostly for use cases involving licensing. One scenario involves running Linux or other non-Windows VMs on Windows Server hosts. These VMs don't require Windows OSE licenses, so why pay for a copy of Windows Server Enterprise or Datacenter editions and their associated licenses when you can host them on Hyper-V Server? A second scenario is for the VDI (virtual desktop infrastructure) scenario. In this scenario, the VMs on the Hyper-V host are running a Windows client, not a Windows Server, so the OSE licenses included with Windows Server Hyper-V are wasted. A similar scenario is of hosting Windows OSes earlier than Windows Server 2008, such as 2003 or 2003 R2.
The last use case is for the "little to no IT" small business scenario. In this case, a Hyper-V host is situated at a small business where some employees are somewhat technical, but not up to the task of virtualization host server management. The bottom line is that you don't want them to logon to the parent partition and inadvertently do anything to harm the host. With a simple command line interface, there's nothing to tweak or otherwise poke around with.
How does Hyper-V Server 2012 compare to VMware's free version of ESXi 5.0, its vSphere Hypervisor 5? vSphere Hypervisor is limited to 4 vCPUs per VM, while Hyper-V Server supports up to 64. Host RAM is limited to 32 GB, while Hyper-V Server supports up to 4 TB. vSphere Hypervisor 5 also contains no VM migration (vMotion), storage migration (Storage vMotion), high availability, extensible switch or VM replication features. It can only be managed by connecting directly to the host with the vSphere client, whereas Hyper-V Server supports both Hyper-V Manager and System Center Virtual Machine Manager remote management.
Hyper-V Replica for Disaster Recovery
Hyper-V Replica provides the ability to take a VM on one Windows Server 2012 Hyper-V host and create a loosely coupled replica on another Windows Server 2012 Hyper-V host. "Loosely coupled" means the replica is not tightly in sync with the source; the latency is approximately five minutes or so when the replication channel is working correctly. With this replica in place, if the source VM fails with no warning, you can bring the replica online and have a very slightly older version available to customers almost immediately. If you have time to gracefully shut down the source VM and replicate its delta to the offsite replica, the failed-over VM will be identical to the source.
This approach sounds like a great idea, but the feature won't be of much use if it has stringent infrastructure requirements. One of the major benefits of Hyper-V Replica is that it doesn't have any dependencies on storage or network infrastructure. One end can have SAN storage with 10 gigabit Ethernet, the other a standalone Hyper-V host with direct attached storage on a 100 Mb network. What does the solution require? Two Windows Server 2012 Hyper-V hosts and network connectivity between them. That's pretty much it. Hyper-V Replica is specifically designed to work over high-latency, restricted bandwidth networks such as WAN circuits to branch offices so you can easily configure replication across the data center, campus, or country.
You're probably already thinking of ways you could use Hyper-V Replica. Offsite replication of a VM to another location is certainly the primary scenario Microsoft designed the feature for; this location could be another site within the company, or at a hosting provider, or even an IaaS cloud. A good small business example would have a business's VMs replicated to their IT provider's own network or data center, so in case of a disaster (or if the small business owner accidently breaks their own VM) a replica will keep the business running. You can also use Hyper-V Replica for planned failover if you're doing host maintenance and don't have a requirement for continuous availability during the maintenance window.
Hyper-V Replica works by first taking a shadow copy of the VM image and transferring it to the replica host. After this setup, the VM is kept up to date by copying a Hyper-V replica log file containing the VM's writes to the replica's host, which applies it to the VM (which is in a shutdown state). As nifty as Hyper-V Replica is, it can't subvert the laws of physics, so it'll obviously take longer for the initial transfer. Thoughtfully, there's an option to perform the initial transfer using external media (e.g. a USB drive) so you can sidestep bandwidth limitations entirely and, for example, hand-carry the image to your Las Vegas replica location. (A useful maxim to remember in IT work is a quote by Andrew S. Tanenbaum, influential professor and author of the classic book Computer Networks: "Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.") Aidan Finn has a nice description of the Hyper-V Replica feature in his blog.
Hyper-V Replica also works with the free Hyper-V Server 2012 product. Assuming you've taken care of the licensing that Hyper-V Server 2012 doesn't provide for, it's a feature-complete version of the hypervisor. You can have virtualization disaster recovery at essentially no cost.
Hyper-V Replica isn't designed to replace clustering, or Live Migration. It's specifically for disaster recovery situations. There's latency between the source and replica VMs of at least five minutes (you can see the actual latency by right-clicking on the replica VM, choosing Replication, and selecting View Replication Health.). Failover is a manual procedure, though I suppose you could script it. It's also not really intended to handle large numbers of VMs.
Microsoft's SMB organization recently published a blog post where Hyper-V Replica did in fact keep two small businesses available during Hurricane Sandy. These customers had recently upgraded to Windows Server 2012, and when they realized the full extent of what was about to hit them in lower Manhattan, they activated Hyper-V Replica and executed a planned failover to their IT service provider's Brooklyn data center. Their actions kept their IT infrastructure up, and employees were able to access the network and work from home the entire time.
I think that Hyper-V Replica provides a strong benefit for small and medium businesses that need disaster recovery capabilities (and don't we all?) but can't afford to spend deeply on infrastructure and software for highly sophisticated solutions. It's yet another tool in the Windows Server 2012 tool chest that makes it such a compelling product for all size companies.
This approach sounds like a great idea, but the feature won't be of much use if it has stringent infrastructure requirements. One of the major benefits of Hyper-V Replica is that it doesn't have any dependencies on storage or network infrastructure. One end can have SAN storage with 10 gigabit Ethernet, the other a standalone Hyper-V host with direct attached storage on a 100 Mb network. What does the solution require? Two Windows Server 2012 Hyper-V hosts and network connectivity between them. That's pretty much it. Hyper-V Replica is specifically designed to work over high-latency, restricted bandwidth networks such as WAN circuits to branch offices so you can easily configure replication across the data center, campus, or country.
You're probably already thinking of ways you could use Hyper-V Replica. Offsite replication of a VM to another location is certainly the primary scenario Microsoft designed the feature for; this location could be another site within the company, or at a hosting provider, or even an IaaS cloud. A good small business example would have a business's VMs replicated to their IT provider's own network or data center, so in case of a disaster (or if the small business owner accidently breaks their own VM) a replica will keep the business running. You can also use Hyper-V Replica for planned failover if you're doing host maintenance and don't have a requirement for continuous availability during the maintenance window.
Hyper-V Replica works by first taking a shadow copy of the VM image and transferring it to the replica host. After this setup, the VM is kept up to date by copying a Hyper-V replica log file containing the VM's writes to the replica's host, which applies it to the VM (which is in a shutdown state). As nifty as Hyper-V Replica is, it can't subvert the laws of physics, so it'll obviously take longer for the initial transfer. Thoughtfully, there's an option to perform the initial transfer using external media (e.g. a USB drive) so you can sidestep bandwidth limitations entirely and, for example, hand-carry the image to your Las Vegas replica location. (A useful maxim to remember in IT work is a quote by Andrew S. Tanenbaum, influential professor and author of the classic book Computer Networks: "Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.") Aidan Finn has a nice description of the Hyper-V Replica feature in his blog.
Hyper-V Replica also works with the free Hyper-V Server 2012 product. Assuming you've taken care of the licensing that Hyper-V Server 2012 doesn't provide for, it's a feature-complete version of the hypervisor. You can have virtualization disaster recovery at essentially no cost.
Hyper-V Replica isn't designed to replace clustering, or Live Migration. It's specifically for disaster recovery situations. There's latency between the source and replica VMs of at least five minutes (you can see the actual latency by right-clicking on the replica VM, choosing Replication, and selecting View Replication Health.). Failover is a manual procedure, though I suppose you could script it. It's also not really intended to handle large numbers of VMs.
Microsoft's SMB organization recently published a blog post where Hyper-V Replica did in fact keep two small businesses available during Hurricane Sandy. These customers had recently upgraded to Windows Server 2012, and when they realized the full extent of what was about to hit them in lower Manhattan, they activated Hyper-V Replica and executed a planned failover to their IT service provider's Brooklyn data center. Their actions kept their IT infrastructure up, and employees were able to access the network and work from home the entire time.
I think that Hyper-V Replica provides a strong benefit for small and medium businesses that need disaster recovery capabilities (and don't we all?) but can't afford to spend deeply on infrastructure and software for highly sophisticated solutions. It's yet another tool in the Windows Server 2012 tool chest that makes it such a compelling product for all size companies.
17 Jan 2013
Windows PowerShell 3.0 simplified syntax
A tip showing an example of how the simplified syntax of Windows PowerShell 3.0 makes commands and scripts easier to read.
One of the improvements in version 3.0 of Windows PowerShell is the simplification of the syntax for the Where-Object cmdlet. For example, to display a list of all installed roles and features on a server, pipe the output of the Get-WindowsFeature cmdlet into the Where-Object cmdlet and use Where-Object to filter out everything except roles and features whose InstallState property is equal to Installed:
Get-WindowsFeature -ComputerName SEA-SRV-1 | Where-Object InstallState -eq Installed
You may have wondered why the above command didn't look like this:
Get-WindowsFeature - ComputerName SEA-SRV-1 | Where-Object {$_.InstallState -eq Installed}
The reason is because Windows PowerShell 3.0 lets you eliminate the script block notation (the curly braces), the current object placeholder ($_), and the dot property notation. These improvements make PowerShell code easier to understand.
One of the improvements in version 3.0 of Windows PowerShell is the simplification of the syntax for the Where-Object cmdlet. For example, to display a list of all installed roles and features on a server, pipe the output of the Get-WindowsFeature cmdlet into the Where-Object cmdlet and use Where-Object to filter out everything except roles and features whose InstallState property is equal to Installed:
Get-WindowsFeature -ComputerName SEA-SRV-1 | Where-Object InstallState -eq Installed
You may have wondered why the above command didn't look like this:
Get-WindowsFeature - ComputerName SEA-SRV-1 | Where-Object {$_.InstallState -eq Installed}
The reason is because Windows PowerShell 3.0 lets you eliminate the script block notation (the curly braces), the current object placeholder ($_), and the dot property notation. These improvements make PowerShell code easier to understand.
15 Jan 2013
Shared Storage Considerations for Hyper-V
One of the biggest considerations that must be taken into account when deploying a Hyper-V server is that of storage. Not only must your server have adequate storage capacity, but the storage subsystem needs to be able to deliver sufficient I/O to meet the virtual machine's demands. Furthermore, storage should offer some sort of redundancy so as to avoid becoming a single point of failure.
As you can imagine, planning for Hyper-V storage is not a task to be taken lightly. Fortunately, there are a lot of options. The trick is to assess the available options and pick a solution that meets your performance, fault tolerance, and budgetary requirements.
My goal in this article is not to discuss every possible storage option for Hyper-V, but rather to give you some insight as to what works and what doesn't work based on my own experiences in the field.
The Most Important Fault Tolerant Consideration
Even though server virtualization is widely regarded as a revolutionary technology, there are a few negative aspects to using it. Perhaps one of the biggest pitfalls to server virtualization is that a single host server runs multiple virtual machines. If the host server were to fail then all of the virtual machines residing on that host also drop offline, resulting in a major outage.
That being the case, I always recommend to my clients that they implement a failover cluster as a way of preventing a host server from becoming a single point of failure. The problem is that failover clustering for Hyper-V requires the use of shared storage, which can be expensive. When Microsoft eventually releases Windows Server 8 and Hyper-V 3.0, the shared storage requirement will go away. For right now though, Hyper-V clusters are often beyond the budget of smaller organizations. Such organizations typically end up using direct attached storage.
Direct Attached Storage
Even though local, direct attached storage does not offer the same degree of redundancy as a full blown clustering solution, it is still possible to build in at least some redundancy by making use of an internal storage array. A storage array won't protect you against a server level failure, but it will protect against a disk failure (if implemented correctly).
Before I talk about your options for RAID storage, I want to talk about a situation that I ran into a few weeks ago. I have a friend who owns a small business and runs three production servers. The servers had been in place for a long time and the hardware was starting to age. My friend didn't really have the money to replace all of the server hardware and asked me if virtualizing the servers might be a good alternative.
After considering my friend's very tight budget and his business needs we decided to purchase a high end PC rather than a true server. The computer had six SATA ports so we planned to use one port for a boot drive, one port for a DVD burner (which was a business requirement), and the remaining four ports for a RAID 5 array.
Even though RAID 5 has fallen out of fashion over the last few years, it made sense in this case because combining the four disks into a RAID 5 array would deliver higher performance (from an I/O prospective) than a mirror set would. Although RAID 5 doesn't perform as well as RAID 0, the built in parity more than makes up for any loss in performance or capacity.
When all of the parts arrived, I set up the new computer in the way that we had planned. However, even though we had built the array from SATA 3 disks which were rated at 6 gigabits per second, the array was painfully slow. In fact, copying files to the array yielded a sustained transfer rate of only about 1 MB per second. Furthermore, the array would almost always fail to copy large files.
I have built similar arrays on comparable hardware in lab environments before, so I knew that the array should perform much better than it was. My initial assumption was that the problem was driver related, but a check of all of the system's drivers revealed that everything was up to date.
The next thing that I decided to do was to update the computer's firmware. Over the years I have had a few bad experiences with firmware updates, so there are a couple of things that I always do prior to updating the firmware. First, I plug the computer into a UPS in case there is a power failure during the update. I have actually had the electricity go out during a firmware update and it ruined the system board.
The other thing that I do is document all of the BIOS settings. While documenting the BIOS settings I noticed that the computer's BIOS had identified all of the hard drives as IDE rather than ACPI. While this could certainly account for the performance problems, the system would not let me set the drives to ACPI.
After a lot of trial and error I discovered that SATA ports one through four could operate in either IDE or ACPI mode, but ports 5 and six could only operate in IDE mode. To fix the problem I moved the boot drive from port 1 to port 5 and moved the DVD burner from port 2 to port 6. I then set ports one through four to use ACPI mode and attached the drives for the storage array.
Before I could use the server, I had to reconfigure the BIOS to boot from the drive on Port 5. I also had to use the Windows Disk Management Console to completely rebuild the RAID array. Once I did that the disk array began delivering the expected level of performance.
The reason why I chose to tell this story is because anyone who decides to store virtual machines on an internal RAID array could potentially run into similar problems. Since I have already worked through the troubleshooting process, I wanted to pass along my solution in the hopes that I could help someone.
RAID Selection
If you end up setting up Hyper-V to use a local RAID array then you will have to decide what type of RAID array you want to use. Your options vary depending on the number of disks that you have to work with. Here are a few thoughts on some common RAID levels:
Using Direct Attached Storage is acceptable for implementing basic server virtualization in a small organization, but is inadequate for use in medium and large sized organizations.
The reason why this is the case has to do with the very nature of server virtualization. Server virtualization uses a single physical server to host multiple virtualized workloads. The problem with doing so is that the cost of failure goes way up. In a physical data center for example, a server failure might be a big inconvenience, but it is rarely catastrophic. Server failures in a virtual data center are another story. If a host server fails then every virtual server residing on that host will also fail. When you consider that a single host might contain dozens of virtual machines you can begin to understand why it is so critically important to protect virtualization hosts.
So what does all this have to do with storage? Well, the only way to protect against a server level failure is to build a failover cluster. If a host within a failover cluster drops off-line then the virtual machines themselves are simply moved to another host that is still functioning. Of course virtual machine migrations can also occur even without a server failure. Often times for example, a virtual machine may be moved to another host in an effort to balance the host workload or in preparation for taking the host off-line for maintenance.
In the Windows Server 2008 and 2008 R2 versions of Hyper-V, the only way to provide virtual machine failover and live migration capabilities is to implement shared storage. Shared storage consists of a storage device that is treated as a local storage resource by all of the nodes in a failover cluster.
Unfortunately shared storage can be expensive to implement. In fact, the cost is one of the major barriers to entry for smaller organizations. Thankfully, Windows Server 2012 will do away with the shared storage requirements for Hyper-V (although shared storage will still be supported).
In the case of Windows Server 2008 and 2008 R2, building a failover cluster for Hyper-V means storing virtual machines on a cluster shared volume. As previously mentioned, the cluster shared volume is networked storage that is accessible to each node in the cluster. The reason why cluster shared volumes tend to be expensive to implement is because the storage must be seen as a local to each cluster node. This rules out connecting cluster nodes to file server storage (although doing so will be supported in Windows Server 2012). For the time being, your only options for implementing shared storage are to use either iSCSI or Fibre Channel.
As is the case for Direct Attached Storage, connectivity is far from being the only consideration that should be taken into account with regard to the storage unit. Other important considerations are the number of IOPS that the storage unit is capable of delivering, resilience to failure, and the bandwidth available for storage connectivity.
When it comes to storage bandwidth, higher bandwidth is obviously better. However, it is important to keep in mind that raw throughput is not always an accurate reflection of storage bandwidth. For example, iSCSI can be utilized over a ten gigabit Ethernet connection. Likewise, there is a flavor of Fibre Channel called Fibre Channel Over Ethernet that can also be used over ten gigabit Ethernet. If one were to only look at raw throughput then it would be easy to assume that Fibre Channel Over Ethernet and iSCSI could both outperform Fibre Channel because Fibre Channel communications are currently limited to 8 gigabits per second. However, Fibre Channel is actually the faster medium in spite of the fact that it has a lower raw throughput. The reason for this is that Fibre Channel Over Ethernet and iSCSI both require storage transmissions to be encapsulated into Ethernet packets. There is quite a bit of overhead associated with the encapsulation process and that overhead causes iSCSI and Fibre Channel Over Ethernet to be slower than Fibre Channel. Network cards with TCP/IP offloading capabilities can help to bridge the gap between the various technologies, but Fibre Channel still comes out ahead.
As previously mentioned, storage bandwidth is not the only consideration that must be taken into account with regard to building a cluster shared volume. IOPS and resiliency to failure are also major concerns. The RAID level used by the storage array directly impacts both of these factors. As a general rule RAID 10 (also called RAID 0+1) is the preferred RAID level because it delivers the highest IOPS while also protecting against hard drive failure.
Implementing a Cluster Shared Volume
The process for creating a cluster shared volume differs depending on what type of storage medium you are using and on whether you are using Windows Server 2008 or Windows Server 2008 R2. As a general rule however, you must begin the process by installing Windows onto each cluster node and then using the Server Manager to deploy the Failover Clustering Service. It is important that each cluster node be configured in an identical manner aside from its computer name and IP addresses.
Once Windows has been installed then the next step in the process is to use an initiator to establish connectivity to the shared storage. Each cluster node must use the same drive letter for the shared storage.
At this point you would open the Failover Cluster Manager and create the cluster. The cluster creation process is beyond the scope of this article since my primary focus is on storage.
Once the cluster has been created, you can select the cluster name within the Failover Cluster Manager and then click on the Enable Cluster Shared Volumes link. When you do, a new container named Cluster Shared Volumes will be created within the console tree. Now you must tell Windows to treat your shared storage as a cluster shared volume. To do so, simply select the Cluster Shared Volume container and then click on the Add Storage link found in the Actions pane. Windows will now ask you which disk you want to use as a cluster shared volume. Make your selection and click OK. The disk that you have selected now appears as a cluster shared volume.
Configuring Virtual Machines to Use the Cluster Shared Volume
After the cluster shared volume is in place the next step is to configure your virtual machines to use it. The first step in doing so is to install Hyper-V onto each cluster node. Once Hyper-V is up and running then you can begin creating virtual machines. As you create the virtual machines you must tell Hyper-V to store the virtual machines and their associated virtual hard disk files on the cluster shared volume. Remember, each cluster node should use the same drive letter for the cluster shared volume.
Believe it or not, merely storing the virtual machine files and the virtual hard disks on the cluster shared volume will not make the virtual machines fault tolerant. To achieve fault tolerance you must shut down the virtual machines (or place them in a saved state) and then take some steps to make the Failover Clustering Service aware of your virtual machines. To do so, open the Failover Cluster Manager and then select the Services and Applications container in the console tree. Next, click the Configure a Service or Application link found in the Actions pane. This will cause Windows to launch the High Availability Wizard.
The wizard's initial screen asks you which service or application you want to configure for high availability. Choose the Virtual Machines option and then click Next. On the following screen select the check boxes that correspond to the virtual machines that you want to add to the failover cluster and click OK. Now just click Next and Finish. When you are done the virtual machines should be listed in the Failover Cluster Manager.
As you can imagine, planning for Hyper-V storage is not a task to be taken lightly. Fortunately, there are a lot of options. The trick is to assess the available options and pick a solution that meets your performance, fault tolerance, and budgetary requirements.
My goal in this article is not to discuss every possible storage option for Hyper-V, but rather to give you some insight as to what works and what doesn't work based on my own experiences in the field.
The Most Important Fault Tolerant Consideration
Even though server virtualization is widely regarded as a revolutionary technology, there are a few negative aspects to using it. Perhaps one of the biggest pitfalls to server virtualization is that a single host server runs multiple virtual machines. If the host server were to fail then all of the virtual machines residing on that host also drop offline, resulting in a major outage.
That being the case, I always recommend to my clients that they implement a failover cluster as a way of preventing a host server from becoming a single point of failure. The problem is that failover clustering for Hyper-V requires the use of shared storage, which can be expensive. When Microsoft eventually releases Windows Server 8 and Hyper-V 3.0, the shared storage requirement will go away. For right now though, Hyper-V clusters are often beyond the budget of smaller organizations. Such organizations typically end up using direct attached storage.
Direct Attached Storage
Even though local, direct attached storage does not offer the same degree of redundancy as a full blown clustering solution, it is still possible to build in at least some redundancy by making use of an internal storage array. A storage array won't protect you against a server level failure, but it will protect against a disk failure (if implemented correctly).
Before I talk about your options for RAID storage, I want to talk about a situation that I ran into a few weeks ago. I have a friend who owns a small business and runs three production servers. The servers had been in place for a long time and the hardware was starting to age. My friend didn't really have the money to replace all of the server hardware and asked me if virtualizing the servers might be a good alternative.
After considering my friend's very tight budget and his business needs we decided to purchase a high end PC rather than a true server. The computer had six SATA ports so we planned to use one port for a boot drive, one port for a DVD burner (which was a business requirement), and the remaining four ports for a RAID 5 array.
Even though RAID 5 has fallen out of fashion over the last few years, it made sense in this case because combining the four disks into a RAID 5 array would deliver higher performance (from an I/O prospective) than a mirror set would. Although RAID 5 doesn't perform as well as RAID 0, the built in parity more than makes up for any loss in performance or capacity.
When all of the parts arrived, I set up the new computer in the way that we had planned. However, even though we had built the array from SATA 3 disks which were rated at 6 gigabits per second, the array was painfully slow. In fact, copying files to the array yielded a sustained transfer rate of only about 1 MB per second. Furthermore, the array would almost always fail to copy large files.
I have built similar arrays on comparable hardware in lab environments before, so I knew that the array should perform much better than it was. My initial assumption was that the problem was driver related, but a check of all of the system's drivers revealed that everything was up to date.
The next thing that I decided to do was to update the computer's firmware. Over the years I have had a few bad experiences with firmware updates, so there are a couple of things that I always do prior to updating the firmware. First, I plug the computer into a UPS in case there is a power failure during the update. I have actually had the electricity go out during a firmware update and it ruined the system board.
The other thing that I do is document all of the BIOS settings. While documenting the BIOS settings I noticed that the computer's BIOS had identified all of the hard drives as IDE rather than ACPI. While this could certainly account for the performance problems, the system would not let me set the drives to ACPI.
After a lot of trial and error I discovered that SATA ports one through four could operate in either IDE or ACPI mode, but ports 5 and six could only operate in IDE mode. To fix the problem I moved the boot drive from port 1 to port 5 and moved the DVD burner from port 2 to port 6. I then set ports one through four to use ACPI mode and attached the drives for the storage array.
Before I could use the server, I had to reconfigure the BIOS to boot from the drive on Port 5. I also had to use the Windows Disk Management Console to completely rebuild the RAID array. Once I did that the disk array began delivering the expected level of performance.
The reason why I chose to tell this story is because anyone who decides to store virtual machines on an internal RAID array could potentially run into similar problems. Since I have already worked through the troubleshooting process, I wanted to pass along my solution in the hopes that I could help someone.
RAID Selection
If you end up setting up Hyper-V to use a local RAID array then you will have to decide what type of RAID array you want to use. Your options vary depending on the number of disks that you have to work with. Here are a few thoughts on some common RAID levels:
| RAID Level | Description | Comments |
| 0 | Striping | RAID 0 delivers high performance, but does not provide any fault tolerance |
| 1 | Mirroring | Disk mirroring is great for redundancy, but RAID 1's performance is almost always inadequate for hosting virtual machines |
| 5 | Striping with parity | RAID 5 delivers the performance of a stripe set (although not as good as RAID 0) and the array can continue functioning even if one disk fails. |
| 6 | Striping with double parity | RAID 6 has a higher degree of overhead than RAID 5 but the array can survive a double disk failure. |
| 10 | Mirrored Stripe Set | RAID 10 (or RAID 1+0 as it is sometimes called) offers the performance of a stripe set, with full mirroring. RAID 10 typically delivers the best bang for the buck, but it takes a lot of hard disks to build an adequately performing RAID 10 array. |
Using Direct Attached Storage is acceptable for implementing basic server virtualization in a small organization, but is inadequate for use in medium and large sized organizations.
The reason why this is the case has to do with the very nature of server virtualization. Server virtualization uses a single physical server to host multiple virtualized workloads. The problem with doing so is that the cost of failure goes way up. In a physical data center for example, a server failure might be a big inconvenience, but it is rarely catastrophic. Server failures in a virtual data center are another story. If a host server fails then every virtual server residing on that host will also fail. When you consider that a single host might contain dozens of virtual machines you can begin to understand why it is so critically important to protect virtualization hosts.
So what does all this have to do with storage? Well, the only way to protect against a server level failure is to build a failover cluster. If a host within a failover cluster drops off-line then the virtual machines themselves are simply moved to another host that is still functioning. Of course virtual machine migrations can also occur even without a server failure. Often times for example, a virtual machine may be moved to another host in an effort to balance the host workload or in preparation for taking the host off-line for maintenance.
In the Windows Server 2008 and 2008 R2 versions of Hyper-V, the only way to provide virtual machine failover and live migration capabilities is to implement shared storage. Shared storage consists of a storage device that is treated as a local storage resource by all of the nodes in a failover cluster.
Unfortunately shared storage can be expensive to implement. In fact, the cost is one of the major barriers to entry for smaller organizations. Thankfully, Windows Server 2012 will do away with the shared storage requirements for Hyper-V (although shared storage will still be supported).
In the case of Windows Server 2008 and 2008 R2, building a failover cluster for Hyper-V means storing virtual machines on a cluster shared volume. As previously mentioned, the cluster shared volume is networked storage that is accessible to each node in the cluster. The reason why cluster shared volumes tend to be expensive to implement is because the storage must be seen as a local to each cluster node. This rules out connecting cluster nodes to file server storage (although doing so will be supported in Windows Server 2012). For the time being, your only options for implementing shared storage are to use either iSCSI or Fibre Channel.
As is the case for Direct Attached Storage, connectivity is far from being the only consideration that should be taken into account with regard to the storage unit. Other important considerations are the number of IOPS that the storage unit is capable of delivering, resilience to failure, and the bandwidth available for storage connectivity.
When it comes to storage bandwidth, higher bandwidth is obviously better. However, it is important to keep in mind that raw throughput is not always an accurate reflection of storage bandwidth. For example, iSCSI can be utilized over a ten gigabit Ethernet connection. Likewise, there is a flavor of Fibre Channel called Fibre Channel Over Ethernet that can also be used over ten gigabit Ethernet. If one were to only look at raw throughput then it would be easy to assume that Fibre Channel Over Ethernet and iSCSI could both outperform Fibre Channel because Fibre Channel communications are currently limited to 8 gigabits per second. However, Fibre Channel is actually the faster medium in spite of the fact that it has a lower raw throughput. The reason for this is that Fibre Channel Over Ethernet and iSCSI both require storage transmissions to be encapsulated into Ethernet packets. There is quite a bit of overhead associated with the encapsulation process and that overhead causes iSCSI and Fibre Channel Over Ethernet to be slower than Fibre Channel. Network cards with TCP/IP offloading capabilities can help to bridge the gap between the various technologies, but Fibre Channel still comes out ahead.
As previously mentioned, storage bandwidth is not the only consideration that must be taken into account with regard to building a cluster shared volume. IOPS and resiliency to failure are also major concerns. The RAID level used by the storage array directly impacts both of these factors. As a general rule RAID 10 (also called RAID 0+1) is the preferred RAID level because it delivers the highest IOPS while also protecting against hard drive failure.
Implementing a Cluster Shared Volume
The process for creating a cluster shared volume differs depending on what type of storage medium you are using and on whether you are using Windows Server 2008 or Windows Server 2008 R2. As a general rule however, you must begin the process by installing Windows onto each cluster node and then using the Server Manager to deploy the Failover Clustering Service. It is important that each cluster node be configured in an identical manner aside from its computer name and IP addresses.
Once Windows has been installed then the next step in the process is to use an initiator to establish connectivity to the shared storage. Each cluster node must use the same drive letter for the shared storage.
At this point you would open the Failover Cluster Manager and create the cluster. The cluster creation process is beyond the scope of this article since my primary focus is on storage.
Once the cluster has been created, you can select the cluster name within the Failover Cluster Manager and then click on the Enable Cluster Shared Volumes link. When you do, a new container named Cluster Shared Volumes will be created within the console tree. Now you must tell Windows to treat your shared storage as a cluster shared volume. To do so, simply select the Cluster Shared Volume container and then click on the Add Storage link found in the Actions pane. Windows will now ask you which disk you want to use as a cluster shared volume. Make your selection and click OK. The disk that you have selected now appears as a cluster shared volume.
Configuring Virtual Machines to Use the Cluster Shared Volume
After the cluster shared volume is in place the next step is to configure your virtual machines to use it. The first step in doing so is to install Hyper-V onto each cluster node. Once Hyper-V is up and running then you can begin creating virtual machines. As you create the virtual machines you must tell Hyper-V to store the virtual machines and their associated virtual hard disk files on the cluster shared volume. Remember, each cluster node should use the same drive letter for the cluster shared volume.
Believe it or not, merely storing the virtual machine files and the virtual hard disks on the cluster shared volume will not make the virtual machines fault tolerant. To achieve fault tolerance you must shut down the virtual machines (or place them in a saved state) and then take some steps to make the Failover Clustering Service aware of your virtual machines. To do so, open the Failover Cluster Manager and then select the Services and Applications container in the console tree. Next, click the Configure a Service or Application link found in the Actions pane. This will cause Windows to launch the High Availability Wizard.
The wizard's initial screen asks you which service or application you want to configure for high availability. Choose the Virtual Machines option and then click Next. On the following screen select the check boxes that correspond to the virtual machines that you want to add to the failover cluster and click OK. Now just click Next and Finish. When you are done the virtual machines should be listed in the Failover Cluster Manager.
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