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|Folder layout of typical Windows 2000/XP user profile. Normally everything except the items within "Local Settings" are stored on the file server as part of a roaming profile.|
A roaming user profile is a concept in the Microsoft Windows NT family of operating systems that allows users with a computer joined to a Windows Server domain to log on to any computer on the same network and access their documents and have a consistent desktop experience, such as applications remembering toolbar positions and preferences, or the desktop appearance staying the same.
All Windows operating systems since Windows NT 3.1 are designed from the start to be able to support roaming profiles. Normally, a standalone computer stores the user's documents, desktop items, application preferences, and desktop appearance on the local computer in two divided sections, consisting of the portion that could roam plus an additional temporary portion containing items such as the web browser cache. The Windows registry is similarly divided to support roaming; there are System and Local Machine hives that stay on the local computer, plus a separate User hive (HKEY CURRENT USER) designed to be able to roam with the user profile.
When a roaming user is created, the user's profile information is instead stored on a centralized file server accessible from any network-joined desktop computer. The login prompt on the local computer checks to see if the user exists in the domain rather than on the local computer; no pre-existing account is required on the local computer. If the domain login is successful, the roaming profile is copied from the central file server to the desktop computer, and a local account is created for the user.
When the user logs off from the desktop computer, the user's roaming profile is merged from the local computer back to the central file server, not including the temporary local profile items. Because this is a merge and not a move/delete, the user's profile information remains on the local computer in addition to being merged to the network.
When the user logs in on a second desktop computer, this process repeats, merging the roaming profile from the server to the second desktop computer, and then merging back from the desktop to the server when the user logs off.
When the user returns to the first desktop computer and logs in, the roaming profile is merged with the previous profile information, replacing it. If profile caching is enabled, the server is capable of merging only the newest files to the local computer, reusing the existing local files that have not changed since the last login, and thereby speeding up the login process.
Due to the profile copying at login and logout, a roaming profile set up using the default configuration can be extremely slow and waste considerable amounts of time for users with large amounts of data in their account.
When Microsoft designed Internet Explorer, the programmers made an explicit decision to store cookies and favorites as tiny individual files less than a kilobyte each, rather than storing this data as a single large consolidated file. Microsoft also stores shortcut files in the Recent profile folder, linking to recently opened files and folders.
File servers tend to only transfer large files several megabytes in size at the fastest possible network speed. Hundreds of very small files only a kilobyte per file can reduce network performance by 90%. As a profile ages and accumulates hundreds to thousands of cookies, favorites, and Recent items, the login and logout times become progressively slower, even though these files occupy only a few megabytes of profile data.
Local caching of the user profile on a desktop computer hard drive can reduce and improve login and logout times, but at the penalty of cluttering up the hard drive with profile data from every cached user who logs in. Local caching is more suitable where people tend to use the same computer every day. Local profile caching is not useful where hundreds to thousands of students need to be able to use any computer across a school or university campus—the cumulative cached data from so many different profiles can consume all available lab computer disk space.
Users with a roaming profile can encounter crippling logon delays when logging in over a WAN. If connected to the domain from a remote site, after authentication, Windows will attempt to pull the user's profile from the location specified in Active Directory. If the location happens to be across a WAN link it can potentially slow the WAN down to a crawl and cause the logon to fail (after a very lengthy delay).
Users with a roaming profile working from a remote site should login to the machine before connecting to the network, (so that the machine uses its cached local copy) and connect to the network after logon has completed. Another option is to remove the roaming profile path from Active Directory prior to their departure. This must be done in enough time that the change is replicated to the relevant Domain Controller at the remote site.
DV video editing in a roaming profile generally results in unacceptably slow login times because the video file segments are also copied back and forth from server to desktop. A one-hour 15 gigabyte DV file takes 20 minutes to copy over a 100 megabit LAN connection. If this were present in a roaming profile it would take at least 20 minutes for the user to log in and 20 minutes to log out.
Even for small DV editing projects consisting of several short source clips, each clip still uses 250 megabytes per minute, and typically the source clips are retained when creating the final DV movie project. A small project consisting of four 5 minute clips to generate one 10 minute movie, totals 7.5 gigabytes of DV data, and requires at least 10 minutes to transfer over a 100 megabit network connection before the user's desktop appears and they can begin to do any work.
In a school environment where such editing projects are not mission-critical and do not absolutely need to be backed up on an expensive tape archive system every night, the applications requiring such excessively large amounts of user data are instead usually run on a stand-alone local account that does not roam, to bypass these network storage and retrieval problems.
Many third-party companies do not understand the difference between the roaming part of the profile and the non-roaming temporary section, and so will store their temporary files in the roaming portion, adding megabytes of unnecessary data to the profile and increasing the roaming login and logout times. Some go as far as intentionally storing data in the wrong location, as a method of encouraging the purchase of more expensive "enterprise" versions of their software (e.g. CounterPath).
In a school environment, roaming can result in severe network congestion and slowness when an entire lab of students log off computers at the same time, and then within minutes are attempting to log in somewhere else. Inconsistency in account data can result if the students begin to log in to the second location before the profile uploading and log out from the first location has finished.
Some programs installed on desktop computers do not properly release control of the User registry during logoff, and can result in corrupted profiles because the User registry copying never successfully completes. To deal with this, Microsoft created a utility known as the User Profile Hive Cleanup Service which will forcefully remap the file handles for these misbehaving programs so that the profile copying can finish successfully and the account logoff is successful. However, the hung program may remain on the local computer still holding the local cached copy of the User registry in a busy state, until the computer is rebooted.
The most recent version of a file in a roaming profile without redirection is stored only on the local computer, and stays there until the user logs off, whereupon it transfers to the server. If nightly server backups are done, and a roaming user does not log off for days at a time, their roaming account documents are not being included in the nightly backup.
Further, if a roaming user uses standby or hibernation to turn off the computer at night, their profile is still not copied to the network. In this manner it is possible for a roaming account's documents to not be backed up for days to weeks at a time, and there is the potential for considerable data loss if the local hard drive suffers a catastrophic failure during these long periods of not logging off the roaming account from the local computer.
Due to the underlying file copying mechanism from server to desktop, roaming assumes the user account is logged on to only a single computer at a time. Documents in a roaming profile copied down to the local machine have no network awareness of each other, and it is not possible to use file locking to alert the user that the file is already open.
Logging onto multiple computers with one account, and opening the same document multiple times on each computer can result in inconsistencies and loss of saved changes if the file is modified on two different computers at the same time:
To deal with these profile copying problems, it is possible to override the default operation of roaming, and set up user accounts so that certain parts of the profile are accessed by the local computer directly on a central file server rather than copying to the local computer first. This requires that the central server and network are extremely reliable and always available, because if the server is down, users can not access their files from a local cached copy.
To the end-user, folder redirection generally does not appear to function any differently from using a normal standalone computer. Redirecting the user's My Documents and Desktop to be accessed directly on a file server are the first two big steps for speeding up roaming profiles. However, as 3rd party software have begun to store more and more data in the Application Data portion of the roaming profile, it has also become useful to redirect that to also be accessed directly on the server.
The question may be raised as to why the entire roaming profile can not be accessed directly on the server, and no copying needs to be done at all. The reasoning for this appears to be that certain Microsoft programs running all the time on the client computer can not tolerate the sudden loss of their data folders if the server goes down or the network is disconnected. Some portions must still be copied back and forth before the desktop appears so that these folders are available if the network-redirected folders go down.
Roaming folder redirection is not compatible with laptop users who take their computer home with them. Normally the entire local cached copy of the profile would be available when the laptop is used away from the building network, but with redirection the most important portions are not stored locally and so are unavailable when used away from the network. Microsoft Direct Access system allows users to connect to the building network over a WAN link transparently.
Redirecting Application Data and logging on multiple times running the same program on each computer can result in corruption of the application settings, due to multiple programs trying to access the same settings files on the server. Some programs such as OpenOffice.org will detect if the preferences are in use somewhere else and alert the user.
Some programs do not work properly with redirected profile folders that refer to a UNC file path on a server share: \\server\share\username\Application Data
These problems with UNC paths can usually be fixed by having the folders redirected to a drive mapping for the UNC share:
However, use of drive mappings is generally deprecated by Microsoft, and UNC-only redirection paths are the preferred implementation.
Folder redirection may be used with mandatory profiles, and is useful in situations where it is desirable to "lock down" the general desktop appearance but still allow users to save documents to the network. For example, this can be used as a generic account for anyone to use without a password for temporary use.
Redirecting My Documents and the Desktop in a mandatory profile will allow documents to be saved, but at logoff, any changes to the desktop appearance such as the desktop picture, Internet Explorer cookies, Favorites, and the Recent documents opened list are reverted to the original state.
A roaming user profile must first be set up on the domain controller to which client computers are joined. In Windows 2000 and later versions, this is set using the Active Directory Users and Computers snap-in. Windows NT 4.0 and earlier used the User Manager for Domains program. A user profile location is set on the server and can be customized, as required. When a user logs onto a domain, the roaming user profile is downloaded from the server onto the local computer and applied. When the user logs off, the changes made to the roaming profile are transferred back to the domain controller.
Although a roaming user profile may be stored in any shared folder of a computer available inside a local Microsoft Windows network, using the domain controller is recommended because the profile data should be available at any workstation the user tries to log on to. Should the server not be available, the user will still be able to log on using a cached copy of the profile on his workstation, unless the profile is super-mandatory.
Enabling roaming profiles for a workstation running Windows NT 4.0, Windows 2000, Windows XP Professional, Windows Vista Business or Ultimate is done by specifying a location on the server where the users' profiles are located; this is done under User Manager for Domains in Windows NT 4.0 Server and Active Directory Users and Computers in Windows 2000 and later. Workstations running Windows 95, 98 or Me can also have roaming profiles, roaming profiles become available in Windows 9x when a home directory on the network is specified for the user and multiple desktop settings have been enabled under the Passwords box in the Windows Control Panel.
Roaming profiles on Windows 95, 98 and Me are all compatible with each other so if a network has mixture of Windows 95 and Windows 98 workstations the same user profile may be used for each workstation. This is also the case with Roaming profiles between Windows NT 4.0, Windows 2000, Windows XP but there may be some compatibility issues due to differences in each version of Windows. Roaming profiles in Windows Vista and Windows 7 are compatible with each other but these versions are not compatible with earlier versions of Windows. A separate profile folder with the extension .V2 will be created when using Roaming profiles with Windows Vista or 7. The easiest solution is to have all workstations running the same version of Windows. (see Compatibility section)
For roaming to work with Novell servers, the Novell product "ZENworks Desktop Management" needs to be installed on the server, and its associated workstation management package installed on each of the client computers. Within the directory, a User Package object is created, which enables roaming, specifies where the roaming profile is stored, and also stores any associated group policies for each version of Windows where users will login. The User Package also enables Dynamic Local User, which functions similar to Active Directory, allowing an account created in eDirectory to log in on any desktop computer even if no local account exists in advance, and assigns local account privileges such as User, Power User, or Administrator to the newly created local user account.
The User Package can be associated with a specific user account in the directory, or is associated with an organizational unit that then applies to all user accounts within that OU. The User Package also enables additional ZENworks Desktop Management functions, such as remote view and remote control of the desktop computer, network printers that follow the user from one desktop to the next, and the scheduling of events that are to be run wherever the user is logged in.
While Windows 3.x does not contain user profiles it was possible for users to have their own personalised desktop in a business environment. Windows 3.x had an administrative setup option which network administrators could use by typing setup.exe /a Windows could then be installed to a network share. Windows setup was then run from each local machine to install a few local files making Windows 3.1 capable of being run over a network. The local files could be saved to a user's home directory on a Novell or Windows NT Domain network allowing the user to have his or her settings roam between machines, the local machine in this scenario did not require a hard drive and could have been booted from a floppy or network card.
Each time a user logs into a workstation, all of the files and settings are transferred over the network; the result is that the login process takes longer than if the user were to use a local profile. This is particularly the case if the profile is large in size. The login time may be reduced if the profile is cached as some files can be loaded from the local workstation and by using folder redirection to redirect folders that can grow to a large size, like My Documents, to a network share.
However, this limitation has been addressed in Windows Server 2008 Active Directory by allowing folder redirection of virtually all folders that were previously stored in a user's profile (including My Music, Favorites, and others) to a centralized and secured network share. This means that a user's roaming profile can easily be reduced to size smaller than 20MB, thus eliminating the long login times that were experienced with previous versions of AD. When using folder redirection and automatic caching of offline files, all of a user's files and preferences are available offline and synced in a much more efficient manner than previously possible when the computer is reconnected to the network using Remote Differential Compression (RDC).
Another problem is related to different set of applications installed on machines, applications stores information into Local Settings and some into the registry, but only the registry is transferred across. It can corrupt application functionality under roaming profile.
While Windows XP and Windows 2000 profiles are basically similar, Windows Vista and its successor Windows 7 use an entirely different profile structure. Windows 8 again uses a different upgraded format. Thus, a user who switches-desk between any combinations of these systems cannot have personal data transferred automatically, as would normally happen with roaming profiles. Instead, two distinct server-side profiles are created for this user in case of XP vs Vista/7 and unpredictable behavior occurs between Windows Vista/7 and Windows 8, since the latter changes the format.
This is an important consideration for any site intending to introduce Vista, Windows 7 or Windows 8 computers into an existing Windows 2000/XP or Windows 7 only roaming-profile network. If possible it should be planned that users will not have to migrate regularly between the two classes of OS.
Windows Vista and 7 will get their profile stored on the server with .V2 added (example: \\server\profiles\username.V2). By default Windows 8 and Windows 8.1 will also use the same format as Windows Vista and 7 unless the individual machine has been configured to use a distinct Windows 8 or Windows 8.1 profile. A distinct Windows 8 profile will use a .V3 extension and Windows 8.1 will use a .V4 extension.
Redirected network folders are able to override the separation between 2000/XP and Vista/Win7. For example, both types of profiles can be redirected to use a single Documents folder, and a single Desktop folder, so that the user's account documents are consistent between the two profiles, even if all other account settings will be different.
Redirected sharing of folders such as Application Data may lead to data corruption, since Microsoft did not intend this for their application data to be shared between the different OS versions.