Optimizing DFS

DFS should be tuned on each replica server using the DFS console. Using the DFS console, the administrator can optimize the replication schedules and connections for DFS targets. On each server, certain existing Registry settings can be optimized, or new settings can be added to change the characteristics or default values of file replication settings, to accommodate the data that is being replicated. These Registry entries include the maximum size of the staging folder. The default setting is 660MB; this value can be increased to 4.2GB.

To increase the staging folder size, update the value data of the Staging Space Limit in KB value in the HKEY_Local_Machine\SYSTEM\CurrentControlSet\Services\NtFrs\ Parameters Registry key. The value entered represents kilobytes. When calculating your limit, remember that 1MB is equal to 1,024KB, not 1,000.

The Windows Server 2003 Resource Kit contains additional tools to optimize FRS connections, and it also includes some DFS and FRS troubleshooting utilities.

Prestaging a New DFS Replica

Windows Server 2003 supports the prestaging of a new target for a replicating DFS link. This provides the ability to restore a copy of an existing replica to this target before replication is enabled. Consider this option when adding existing DFS replicas containing large amounts of data because performing a full replication could severely impact network performance. This process is fairly straightforward if the right tools are used.

To prestage a DFS replica, follow these steps:

1.	Back up a single target of a replicating DFS link using the Windows Server 2003 Backup utility (ntbackup.exe).
2.	On the new target server, create the folder and file share for the new DFS target and set permissions accordingly. Most likely, the share and root folder NTFS permissions on an existing target are correct, so the permissions for this new target should mimic the existing targets.
3.	Using the Windows Server 2003 Backup utility, restore the previously backed-up target data to the target folder on the new server using the Restore to Alternate Location option. For more information regarding restoring data to an alternate location using Windows Server 2003 Backup, refer to Chapter 33, "Recovering from a Disaster."
4.	Using the DFS console logged in with an account with the proper permissions, add this target to the link if it has not already been added.

If one of the predefined replication topology choices has been configured for this link (for example, hub-and-spoke, ring, or full mesh), the new target will be added to the replication immediately. If a customized replication topology was previously created, you must add the new target to the replication manually by creating new replication connections for it.

This process currently works only if the data is backed up and restored using Windows Server 2003 Backup. When the new target is added to the replication, all the restored files are moved into the pre-existing folder within the target. FRS then compares the files in the pre-existing directory with the information provided by the existing targets. When a file is identified to be the same file as on the existing target, it is moved out of the preexisting folder to the proper location in the target. Only files that have changed or been created since the backup are replicated across the network.