Computer Enterprise: Windows User State Virtualization

Planning USV for Mixed Windows Versions

As described in the first article of this series, Windows Vista introduced a new "v.2" user profile that has a flattened folder structure that separates user data and settings better than the Windows XP user profile did. As a result of this change, older Windows XP user profiles are not compatible with the newer v.2 profiles of Windows Vista. This means that you can't use Roaming User Profiles (RUP) as a solution for roaming between computers running Windows Vista and Windows XP. If you try to implement RUP in a mixed XP/Vista environment, users who roam between the two OS versions will end up with two separate profiles on the RUP server, one profile for XP computers and the other for Vista computers.

No changes were made to user profiles in Windows 7 and the user profile structure in Windows 7 is identical to that in Windows Vista. This means you can use RUP to enable users to roam between computers running Windows 7 and Windows Vista provided there are no other architecture or application-specific issues as described in the sections below. It also means that you can't use RUP to roam between Windows 7 and Windows XP computers.

If users do need to roam between computers running Windows XP and computers running later versions of Windows, you can use Folder Redirection (FR) with Offline Files (OF) enabled to redirect Documents and other folders where users store work-related data. This allows user data to be accessible from computers running any version of Windows. You cannot roam user settings however, since user settings resides in both the AppData\Roaming folder and in the Ntuser.dat file (the HKCU registry hive) in the root of the user's profile. Since RUP cannot be used in this scenario, and since AppData\Roaming should never be redirected unless you also use RUP, this means only user data can be roamed in this scenario, not user settings. Table 1 summarizes a USV strategy for mixed environments running different versions of Windows on different computers.

OS versions	RUP	FR with OF
XP and Win7	No	Yes (data folders only)
XP and Vista	No	Yes (data folders only)
Vista and Win7	Yes	Yes

Table 1: USV strategy for mixed environment having different Windows versions on different computers

If you plan on implementing FR in a mixed XP and Win7 (or mixed XP and Vista) environment and you need to redirect the Pictures, Music or Videos folder, you will need to select the Follow The Documents Folder option on the Target tab of the redirection policy for these folders (see Figure 1). Doing this will cause these folders to be redirected as subfolders of the Documents folders (as in XP) instead of as peers of the Documents folder (as in Vista and later) and causes these folders to inherit their redirection settings from the Documents folder instead of having this configured on the folders themselves. Don't do this however unless you have users who still need to access their redirected data folders from computers running Windows XP since choosing this option alters the structure of the user's profile. If users only need to access redirected data from computers running Windows Vista or later then don't select Follow The Documents Folder when redirecting the Pictures, Music or Videos folders. And in any case, you shouldn't redirect these particular folders at all unless there is a business need for these folders to be redirected (such as centrally backing up internally developed training videos or in-house developed graphics).

Figure 1: Configuring redirection on Pictures to follow Documents

Alternatively, instead of selecting Follow The Documents Folder individually for the Pictures, Music and Videos folders, you can simply select Also Apply Redirection Policy To Windows 2000, Windows 2000 Server, Windows XP and Windows Server 2003 Operating Systems on the Settings tab as shown in Figure 2 as this has the effect of automatically configuring the Pictures, Music and Videos folders to Follow The Documents Folder.

Figure 2: Enabling this setting causes Pictures, Music and Videos to follow Documents.

Planning USV for Mixed Windows Architectures

Beginning with Windows Vista two hardware architectures have been available for Windows platforms: x86 (32-bit) and x64 (64-bit). An x64 version of Windows XP was also released but was never widely deployed, largely due to lack of device driver support, so we won't be considering Windows XP x64 in this discussion.

While the underlying user profile folder structure of Windows 7 x86 (or Windows Vista x86) and Windows 7 x64 (or Windows Vista x64) are identical, there are differences in how the Windows registry is structured on x86 and x64 versions of Windows. Specifically, the registry on x64 Windows also contains the x86 registry structure, but the reverse isn't true—the registry on x86 Windows does not contain any x64 registry structure. Another issue is that the location of some programs are stored in the registry using static paths such as C:\Program Files or C:\Program Files (x86), and this means when you try roaming between 32-bit and 64-bit machines these registry items will typically cause problems. The result of these differences is that you can't use RUP to roam users between computers running Windows 7 x86 (or Windows Vista x86) and computers running Windows 7 x64 (or Windows Vista x64).

However, if users do need to roam between computers running x86 and x64 versions of Windows, you can use FR with OF to redirect Documents and other data folders to allow work-related data to be accessible to users from computers running both x86 and x64 versions of Windows. You cannot roam user settings however since user settings in HKCU on a computer running an x64 version of Windows are not compatible with user settings in HKCU on a computer running an x86 version of Windows. Table 2 summarizes a USV strategy for mixed environments running x86 versions of Windows one some computers and x64 versions of Windows on others.

OS architectures	RUP	FR with OF
Win7 x86 and Win7 x64	No	Yes (data folders only)
Vista x86 and Vista x64	No	Yes (data folders only)

Table 2: USV strategy for mixed environment having both x86 and x64 versions of Windows on different computers

Planning USV for Mixed Application Versions/Architectures

Issues involving applications in roaming environment are similar to those involving Windows versions. For example, say you have Windows Vista on some computers and Windows 7 on others. You also have version N of an application installed on the Vista machines, but have the newer version N+1 of the same app installed on the Windows 7 machines. If you implement RUP and/or FR/OF in such an environment, can you expect users to experience any problems when they work with this application?

Probably. It's likely that the new version of the app has more features than the old one, and new features will undoubtedly mean new per-user registry settings and possibly new user settings stored as files under the AppData\Roaming folder. What happens when registry settings or AppData\Roaming files used by the new version of the app are loaded by the old version of the app? Who knows! The only way you can be sure if this scenario will work is to test, test and test before you deploy your USV solution in your production environment. Otherwise, users may find that certain apps they use crash or hang unexpectedly, or behave in strange and unpredictable ways. Such a scenario could even cause users lose data or cause data to be corrupted. It's best to play it safe and make sure that, regardless of which version of Windows is running on each computer, the same version of each app is installed. Be kind to your helpdesk personnel and don't let them be inundated with complaints from angry users.

This is even more true with different architecture versions (x86 or x64) of applications. For example, say you have the x64 version of a particular application installed on Windows 7 x64 computers and the x86 version of the same application installed on Windows Vista x64 computers. The OS architectures are both x64 which supports a RUP scenario, but it's likely that the x86 and x64 versions of the application store their settings in different parts of HKCU and maybe even different folders and files in the AppData\Roaming folder. This means the same kind of frustrating, unpredictable behavior may occur if users try to work on the same data file from one computer running the x86 version of the app and then later on a second computer running the x64 version of the app. Even worse, the data file being worked on might become corrupted. I'm not saying this will happen for sure, and the only way to know for sure is to test, test and test again. But it's better to play it safe and simply standardize all your computers on either the x86 or x64 version of the app. This may not be a big issue today since 64-bit apps like the 64-bit version of Office 2010 are just now appearing, but in the future it's likely to be a concern as more and more software vendors start releasing 64-bit versions of apps that had until now only been available in 32-bit form. Table 3 summarizes a USV strategy for mixed environments running different versions/architectures of applications on different computers.

App versions/architectures	RUP	FR with OF
Multiple different versions of the same app	Play it safe—don't use RUP	Yes (data folders only)
Both x86 and x64 versions of the same app	Play it safe—don't use RUP	Yes (data folders only)

Table 3: USV strategy for mixed environment having different application versions/architectures on different computers

If there is a clear business need to provide users with multiple versions of applications or even different architecture versions of applications, you should consider implementing one of the following application virtualization solutions from Microsoft (choose the one that meets your need in terms of functionality and manageability):