Distributed File System

Distributed File System overview With Distributed File System (DFS), system administrators can make it easy for users to access and manage files that are physically distributed across a network. With DFS, you can make files distributed across multiple servers appear to users as if they reside in one place on the network. Users no longer need to know and specify the actual physical location of files in order to access them. For example, if you have marketing material scattered across multiple servers in a domain, you can use DFS to make it appear as though all of the material resides on a single server. This eliminates the need for users to go to multiple locations on the network to find the information they need. Reasons for using DFS You should consider implementing DFS if: • You expect to add file servers or modify file locations. • Users who access targets are distributed across a site or sites. • Most users require access to multiple targets. • Server load balancing could be improved by redistributing targets. • Users require uninterrupted access to targets. • Your organization has Web sites for either internal or external use. DFS types You can implement a distributed file system in either of two ways, either as a stand-alone root distributed file system, or as a domain distributed file system. Accessing DFS targets from other computers In addition to the server-based DFS component of the Windows Server 2003 family, there is a client-based DFS component. The DFS client caches a referral to a DFS root or a DFS link for a specific length of time, defined by the administrator. The DFS client component runs on a number of different Windows platforms. For information on DFS client versions and their associated platforms. Platform compatibility The Windows Server 2003 family supports targets on the following platforms. Platform Host DFS Client Host DFS Root MS-DOS, Windows 3.x, Windows for Workgroups, and NetWare servers No No Windows 95 Yes, download client No Windows 98 Yes, stand-alone client included; download client for domain No Windows NT 4.0 and Service Pack 3 Yes, stand-alone client included Yes, stand-alone root DFS only Windows 2000 and the Windows Server 2003 family Yes, client included Yes, stand-alone and domain DFS Note • To support synchronization of targets, the referenced resource for a target must be located on a Windows Server 2003 family NTFS partition. Distributed File System features The Distributed File System (DFS) provides several important features, described in the following sections. Easy access to files A distributed file system makes it easier for users to access files. Users need only go to one location on the network to access files, even though the files may be physically spread across multiple servers. Also, when you change the physical location of a target, user access to the folder is not impacted. They still access the folder in the same way as before, because the location of the file looks the same. Users no longer need multiple drive mappings to access their files. Finally, scheduled file server maintenance, software upgrades and other tasks that normally require taking the server offline can be accomplished without disrupting user access. This is particularly useful for Web servers. By selecting the root for the Web site as a DFS root, you can move resources within the distributed file system without breaking any HTML links. Availability Domain DFS ensures that users retain access to their files, in two ways: First, the Windows Server 2003 operating system automatically publishes the DFS mapping to Active Directory. This ensures that the DFS namespace is always visible to users on all servers in the domain. Second, as an administrator, you can replicate your DFS roots and your targets. Replication means that you can duplicate DFS roots and targets on multiple servers in the domain. In this way, users can still access their files, even if one of the physical servers on which those files reside becomes unavailable. Server load balancing A DFS root can support multiple targets that are physically distributed across a network. This is useful, for example, if you have a file that you know will be accessed heavily by your users. Rather than all users physically accessing this file on a single server, and thus taxing the server, DFS ensures that user access to the file is distributed to multiple servers. To users, however, the file resides in one location on the network. File and folder security Because the shared resources DFS manages use standard NTFS and file sharing permissions, you can use preexisting security groups and user accounts to ensure that only authorized users have access to sensitive data. Distributed File System mapping A Distributed File System (DFS) mapping consists of a DFS root, one or more DFS links, and referrals to one or more targets. The domain server on which a DFS root resides is known as a host server. You can replicate a DFS root by creating root targets on other servers in the domain. This provides file availability when the host server becomes unavailable. To users, a DFS mapping provides unified and transparent access to the network resources they need. To system administrators, a DFS mapping is a single DNS namespace: With domain DFS, the DNS names for the DFS root targets resolve to the host servers for the DFS root. Because the host server for a domain distributed file system is a member server within a domain, the DFS mapping is automatically published to Active Directory by default, thus providing synchronization of DFS topologies across host servers. This, in turn, provides fault tolerance for the DFS root and supports optional replication of targets. You can expand a DFS mapping by adding a DFS link to the DFS root. The only constraint on the number of hierarchical levels in a DFS mapping is imposed by the Windows Server 2003 family limit of 260 characters for any file path. A new DFS link can refer to a target with or without subfolders, or to an entire Windows Server 2003 family volume. If you have adequate permissions, you can also access any local subfolders that exist in or are added to a target. Best practices • Use DFS with the NTFS file system only. Do not install DFS on a FAT file system. DFS on the Windows Server 2003 family can only be used with the NTFS file system. For information on converting a volume to NTFS, seeConvert. • Set the replication policy. To maintain a balanced load on your server, you should consider the schedule of synchronization. This requires that you understand the following: o The topology between the participating servers. o How network performance may be impacted, based on available bandwidth. o The quantity of replication traffic likely to occur. o Replication schedules for the distributed file system, as well as the replication schedules for any other distributed file systems in the same site. Automatic file replication through the File Replication service (FRS) is only available with domain DFS. • Do not create FRS replica sets on a volume that is managed by Remote Storage. Doing so might severely impact system performance and possibly cause data loss within your media library. FRS might need to periodically read every file in the replica set to send the file contents to another computer. This causes FRS to recall all files that Remote Storage has sent to secondary storage, which might take a long time (hours or days). If you use tape for your secondary storage, remember FRS recalls files in directory order rather than media order, so the excessive number of tape seeks performed by FRS will likely ruin the tapes and cause data loss. • Perform regular administration as follows: After you have created a DFS console for the DFS roots that you administer, save the console file for future use. Periodically, perform a status check on common targets to ensure that the targets are still accessible. • Ensure that file system permissions are set correctly. In order for a user to access files in a DFS target folder, the user must be allowed access to the target and to all parent folders. In addition, the user must be allowed access to the server hosting the DFS root, and to the link and the link's parent folders. For more information on setting permissions, see Access control overview. • Monitor anti-virus or defragmentation software carefully. Anti-virus and defragmentation software can interfere with successful file replication. If you are running anti-virus or defragmentation software on any of the computers that host your domain DFS root or targets, disable it or monitor it carefully until initial file replication is complete. • Consider the needs of your users. Include commonly-used network shares in your DFS namespace. For links that point to targets with content that frequently changes,use a shorter cache time-out value to ensure that clients maintain an updated list of targets To create a DFS root 1. Open Distributed File System. 2. On the Action menu, click New Root. 3. Follow the instructions that appear in the New Root wizard. Notes • In order to make changes to an existing DFS namespace, you must be a member of the Administrators group on the server hosting the namespace. As a security best practice, consider using Run as to perform this procedure. For more information, see Default local groups, Default groups, and Using Run as. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • If the folder that you specify to correspond to the root does not exist, or has not been shared, you will be prompted to create a new shared folder. You can then type the name of a new folder, or type the name of an existing folder that has not yet been shared. DFS will create the folder (if necessary), then share the folder. • You can host multiple DFS roots on a single computer when using Windows Server 2003, Enterprise Edition, or Windows Server 2003, Datacenter Edition. • On server clusters, the name you give a non-clustered DFS root on a node's local storage must be different from the name you give a clustered DFS root on the cluster storage. • To remove a root, select the root, open the Action menu, and click Delete Root. • Any member server or domain controller can host a DFS root. You must have be a member of the Administrators group on a server to create a DFS root on that server. In addition, you need domain administrator credentials to create a domain root. • If your DFS namespace includes roots and root targets which exist on both computers running one of the Windows Server 2003 family of products and computers running Windows 2000, you must administer those roots from a computer running a product in the Windows Server 2003 family, or from a computer running the Windows Server 2003 Administration Tools Pack. You can not administer the DFS namespace from a computer running Windows 2000. • Only NTFS volumes can host DFS roots. You cannot host a DFS root on a FAT or FAT32 partition. • When working with shared folders, use NTFS and file sharing permissions to secure the folder and any subfolders so that only authorized users can access them. To add a DFS root target 1. Open Distributed File System. 2. Select the domain root for which you want to add a root target. 3. On the Action menu, click New Root Target. 4. Follow the instructions that appear in the New Root wizard. Notes • In order to make changes to an existing DFS namespace, you must be a member of the Administrators group on the server hosting the namespace. As a security best practice, consider using Run as to perform this procedure. You must be a member of the Administrators group on a server to create a root target on that server. For more information, see Default local groups, Default groups, and Using Run as. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • To remove a root target, select the root target, open the Action menu, and click Remove Target. • You can only add root targets to domain DFS roots. • If the folder that you specify to correspond to the root target does not exist or has not been shared, you will be prompted to create a new shared file. You can then type the name of a new folder, or type the name of an existing folder that has not yet been shared. DFS will create the folder (if necessary), then share the folder. Be aware that although the name of the folder itself does not have to be the same as the root, the folder will automatically be shared with the same name as the root. • If you add a shared folder on a Windows 2000 computer as a root target, it may not display in the list of root targets immediately. • If your DFS namespace includes roots and root targets which exist on both computers running one of the Windows Server 2003 family of products and computers running Windows 2000, you must administer those roots from a computer running a product in the Windows Server 2003 family, or from a computer running the Windows Server 2003 Administration Tools Pack. You can not administer the DFS namespace from a computer running Windows 2000. • When working with shared folders, use NTFS and file sharing permissions to secure the folder and any subfolders so that only authorized users can access them. To show a DFS root 1. Open Distributed File System. 2. Click Distributed File System. 3. On the Action menu, click Show Root. 4. In the Root or host server field, type in the UNC name for an existing DFS root, or expand the list of trusting domains and click the DFS root, then click OK. Notes • To perform this procedure, you must be a member of the Administrators group on the local computer, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members of the Domain Admins group might be able to perform this procedure. As a security best practice, consider using Run as to perform this procedure. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • To specify the DFS root, you can type either \\HostDomain\DFSRootName or \\HostServer\DFSRootName, where HostDomain is the name of the domain on which the root resides (for domain DFS), HostServer is the name of the server on which the root resides (for stand-alone DFS), and DFSRootName is the name of the root. • You can also show a root by typing the name of the host server alone. If the host server has a single root, DFS will show the root. If the host server has multiple roots, DFS will display a list of all the roots on the server and allow you to pick the root or roots to display. You can select more than one root by holding down the SHIFT or CTRL keys as you click. To add a DFS link 1. Open Distributed File System. 2. In the console tree, click the DFS root. 3. On the Action menu, click New Link. 4. Type a name for the new link. 5. Type a path for the new link or click Browse to select from the list of available shared folders. 6. Type a comment, if you would like to use it to further identify or describe the link. 7. Type the duration for which a reference to this link will be cached on a DFS client, then clickOK. Notes • In order to make changes to an existing DFS namespace, you must be a member of the Administrators group on the server hosting the namespace. As a security best practice, consider using Run as to perform this procedure. For more information, see Default local groups, Default groups, and Using Run as. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • The folder that you specify as the target must be an existing shared folder. • To delete a link, select the link, open the Action menu, and click Delete Link. • If you later delete a target from this link using dfscmd /remove on the command line, you must specify the same name you used to create the link. For example, if you create the link using its DNS name, you must specify the DNS name when using dfscmd, rather than the NetBIOS name. Consider using a consistent naming standard when adding links, so it will be easier to remember later. • When working with shared folders, use NTFS and file sharing permissions to secure the folder and any subfolders so that only authorized users can access them. To filter the DFS link display 1. Open Distributed File System. 2. In the console tree, click the DFS root. 3. On the Action menu, click Filter Links. 4. In the Type the maximum number of links box, type the maximum number of links to display in the console tree. 5. Select Filter links by name, and then do one of the following: o To display all links with names starting with a certain text string, select Starts with in the list box, and then type the text string on which you would like to filter. o To display all links with names containing a certain text string, select Contains in the list box, and then type the text string on which you want to filter. Notes • To perform this procedure, you must be a member of the Administrators group on the local computer, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members of the Domain Admins group might be able to perform this procedure. As a security best practice, consider using Run as to perform this procedure. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • To display all DFS links, type a number greater than or equal to the total number of existing links in the Type the maximum number of links box, and select Do not filter links by name. To enable or disable DFS referral 1. Open Distributed File System. 2. In the console tree, click the DFS link that points to the target for which you would like to change the referral status. 3. Click the desired target. On the Action menu, select Enable or Disable Referral. Notes • In order to make changes to an existing DFS namespace, you must be a member of the Administrators group on the server hosting the namespace. As a security best practice, consider using Run as to perform this procedure. For more information, see Default local groups, Default groups, and Using Run as. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • When you disable DFS referral for a target, DFS will not direct users to the target folder until DFS referral is enabled. • If DFS referral is enabled for a target, selecting Enable or Disable Referral will disable it. If DFS referral is disabled, the action will enable it. • The DFS Referral column and Status column in the details pane provide information about the referral status of each target. The DFS Referral column indicates if DFS referral is enabled and the Status column indicates if a particular target is available. If a target can not accessed, the Status column will read Offline. To see the current status for a target, click it and select Check Status from the Action menu. • When working with shared folders, use NTFS and file sharing permissions to secure the folder and any subfolders so that only authorized users can access them. To add a target 1. Open Distributed File System. 2. In the console tree, click the DFS link to which you want to assign a target. 3. On the Action menu, click New Target. 4. Under Path to target (shared folder), enter the name of a shared folder, or click Browseto select from the list of available shared folders. 5. If you are adding the target to a domain root, click Add this target to the replication setto enable automatic file replication for the target. 6. If you are not enabling automatic file replication, you must manually copy files to the new target from other targets. Notes • In order to make changes to an existing DFS namespace, you must be a member of the Administrators group on the server hosting the namespace. As a security best practice, consider using Run as to perform this procedure. For more information, see Default local groups, Default groups, and Using Run as. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • The folder that you specify as the target must be an existing shared folder. • To remove a target, select the target, open the Action menu, and click Remove Target. • This procedure for adding a target should not be used for adding the first target. The first target is added when you create the DFS link. • If a link points to another domain DFS, it cannot point to any other targets. To add a target in this case, you must add it to the targeted DFS and not to the link itself. • Automatic file replication through the File Replication service is only available with domain DFS. • When working with shared folders, use NTFS and file sharing permissions to secure the folder and any subfolders so that only authorized users can access them. To check status of a DFS root, DFS link, or target 1. Open Distributed File System. 2. In the DFS administration tool, click the DFS root, DFS link, or target whose status you want to check. 3. On the Action menu, click Check Status. Notes • To perform this procedure, you must be a member of the Administrators group on the local computer, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members of the Domain Admins group might be able to perform this procedure. As a security best practice, consider using Run as to perform this procedure. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. To hide a DFS root 1. Open Distributed File System. 2. In the console tree, click the DFS root. 3. On the Action menu, click Hide Root. 4. A dialog box will appear, asking if you want to hide the root. Click Yes. Notes • To perform this procedure, you must be a member of the Administrators group on the local computer, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members of the Domain Admins group might be able to perform this procedure. As a security best practice, consider using Run as to perform this procedure. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • The root is removed from the DFS administration tool. The distributed file system itself is not affected. User access to the root is not affected by this procedure. To delete a DFS root, root target, link, or target 1. Open Distributed File System. 2. Click the DFS root, root target, link, or target that you want to delete. You might have to navigate through the console tree to reveal the object you would like to delete. 3. On the Action menu, click Delete Root, Delete Link, or Remove Target, depending on the nature of the object you would like to delete. 4. A dialog box will appear asking you for confirmation. Click Yes. Important • Deleting a root is not a recoverable operation. Deleting a root removes the root from the administration tool and removes the entire DFS structure associated with the root, but does not delete any data. If it is a stand-alone root, the procedure removes the DFS configuration data from the host computer. If it is a domain root, the procedure removes the configuration data from each host computer and from Active Directory. • Deleting a root, root target, link, or target does not delete any associated shared folders from the file system, and it does not change any permissions associated with files or folders. If you no longer want users to have access to data in these shared folders, use NTFS or file sharing permissions to restrict access. Notes • In order to make changes to an existing DFS namespace, you must be a member of the Administrators group on the server hosting the namespace. As a security best practice, consider using Run as to perform this procedure. For more information, see Default local groups, Default groups, and Using Run as. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • If you remove the only target of a link, the link will be deleted. Configure replication • View replication properties • Initiate file replication • Show or hide replication information for a list of targets • Enable or disable replication for a target • Modify replication topology • Set the replication schedule • Exclude files or subfolders from replication • Remove files or subfolders from the exclusion list To view replication properties 1. Open Distributed File System. 2. Click the domain DFS root or link for which replication has been configured. 3. On the Action menu, click Properties. 4. Click the Replication tab. Caution • Do not create File Replication service (FRS) replica sets on a volume that is managed by Remote Storage. Otherwise you might severely impact system performance and possibly cause data loss within your media library. FRS might need to periodically read every file in the replica set to send the file contents to another computer. This causes FRS to recall all files that Remote Storage has sent to secondary storage, which might take a long time (hours or days). If you use tape for your secondary storage, remember FRS recalls files in directory order rather than media order, so the excessive number of tape seeks performed by FRS will likely ruin the tapes and cause data loss. Notes • To perform this procedure, you must be a member of the Administrators group on the local computer, or you must have been delegated the appropriate authority. If the computer is joined to a domain, members of the Domain Admins group might be able to perform this procedure. As a security best practice, consider using Run as to perform this procedure. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • This procedure is applicable only after you have initiated replication. • Automatic file replication through the File Replication service is only available with domain DFS. • From here, you can view and change the replication topology, view and change the replication schedule, and exclude files and subfolders from replication. To initiate file replication 1. Open Distributed File System. 2. Click the domain root or link for which you would like to initiate replication. 3. On the Action menu, select Configure Replication. 4. Follow the instructions that appear in the Configure Replication wizard. Caution • Do not create File Replication service (FRS) replica sets on a volume that is managed by Remote Storage. Otherwise you might severely impact system performance and possibly cause data loss within your media library. FRS might need to periodically read every file in the replica set to send the file contents to another computer. This causes FRS to recall all files that Remote Storage has sent to secondary storage, which might take a long time (hours or days). If you use tape for your secondary storage, remember FRS recalls files in directory order rather than media order, so the excessive number of tape seeks performed by FRS will likely ruin the tapes and cause data loss. • Do not enable replication on Distributed File System (DFS) roots. Notes • To perform this procedure, you must be a member of the Domain Admins group in Active Directory, or you must have been delegated the appropriate authority. As a security best practice, consider using Run as to perform this procedure. For more information, see Default local groups, Default groups, and Using Run as. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • Automatic file replication through the File Replication service is only available with domain DFS. • A domain DFS root or link must have at least two targets before you can begin replication. • To stop replication on a link, click the link, click the Action menu, and then click Stop Replication. To show or hide replication information for a list of targets 1. Open Distributed File System. 2. Click the DFS link for which you want to display or hide replication information. 3. On the Action menu, click Show Replication Information (if the "File Replication" column is currently hidden and you want to display it) or Hide Replication Information (if the "File Replication" column is currently visible and you want to hide it). Caution • Do not create File Replication service (FRS) replica sets on a volume that is managed by Remote Storage. Otherwise you might severely impact system performance and possibly cause data loss within your media library. FRS might need to periodically read every file in the replica set to send the file contents to another computer. This causes FRS to recall all files that Remote Storage has sent to secondary storage, which might take a long time (hours or days). If you use tape for your secondary storage, remember FRS recalls files in directory order rather than media order, so the excessive number of tape seeks performed by FRS will likely ruin the tapes and cause data loss. To enable or disable replication for a target 1. Open Distributed File System. 2. Click the DFS link for which you want to manage replication. 3. If the "File Replication" column is not visible in the list of targets, display it by clicking theAction menu and clicking Show Replication Information. 4. Click the target for which you would like to change the replication status. 5. On the Action menu, click Enable Replication (if replication is currently disabled and you want to enable it) or Disable Replication (if replication is currently enabled and you want to disable it). If you are enabling replication for the target, you will be prompted to designate a staging folder. Caution • Do not create File Replication service (FRS) replica sets on a volume that is managed by Remote Storage. Otherwise you might severely impact system performance and possibly cause data loss within your media library. FRS might need to periodically read every file in the replica set to send the file contents to another computer. This causes FRS to recall all files that Remote Storage has sent to secondary storage, which might take a long time (hours or days). If you use tape for your secondary storage, remember FRS recalls files in directory order rather than media order, so the excessive number of tape seeks performed by FRS will likely ruin the tapes and cause data loss. Notes • To perform this procedure, you must be a member of the Domain Admins group in Active Directory, or you must have been delegated the appropriate authority. As a security best practice, consider using Run as to perform this procedure. For more information, see Default local groups, Default groups, and Using Run as. • To open DFS, click Start, click Control Panel, double-click Administrative Tools, and then double-click Distributed File System. • Automatic file replication through the File Replication service is only available with domain DFS. • You cannot disable replication on a target that is serving as the hub in a hub-and-spoke replication system without first designating a different target as a hub. To modify replication topology 1. Open Distributed File System. 2. Click the root or link for which you want to manage replication. 3. On the Action menu, click Properties. 4. On the Replication tab, click the Customize button. 5. In the Topology drop-down list, click the type of replication topology you want to use. A list of server connections will appear under Connections. 6. Under Connections, select or clear the check boxes to enable or disable replication connections between servers. 7. If you choose a custom topology, you must add and delete connections manually. To add a connection, click the New button, or, to delete an existing connection, click Delete. 8. To change the synchronization priority for initial synchronization or restores, click thePriorities button. • The Replication tab is only available for domain DFS roots or links for which you have already configured replication. To exclude files or subfolders from replication 1. Open Distributed File System. 2. Click the domain DFS root or link for which you want to manage replication. On the Actionmenu, click Properties. 3. On the Replication tab, next to File filter (for files) or Subfolder filter (for subfolders), click Edit. 4. Type the name of a file or subfolder you want to exclude from replication. 5. Click Add to add the file or folder name to the exclusion list, and then click OK. To set the replication schedule 1. Open Distributed File System. 2. Click the domain DFS root or link for which you want to manage replication. On the Actionmenu, click Properties. 3. On the Replication tab, click Schedule. The replication schedule appears, with blue representing the times when replication is available, and white representing the times when replication is not available. 4. On the replication schedule, click to select an hour or drag to select a range of hours. 5. Enable or disable replication for the selected time period or periods as follows: o To enable replication, click Replication Available. o To disable replication, click Replication Not Available 6. Repeat the previous two steps as necessary, then click OK. To remove files or subfolders from the exclusion list 1. Open Distributed File System. 2. Click the domain DFS root or link for which you want to manage replication. On the Actionmenu, click Properties. 3. On the Replication tab, next to File filter or Subfolder filter, click Edit. 4. Click the file or folder name or specification you would like to remove from the list. 5. Click Remove to remove the item from the exclusion list, and then click OK.