Configuring Correct Staging Area Space for Replica Sets


This article describes the correct staging area space for replica sets. The File Replication service (FRS) creates staging files to replicate data among replica set members. It is important to allocate enough staging area space. If you do not have enough staging area space, various problems may occur.

More Information

The Staging folder stores modified files temporarily before they are propagated to other replication partners. The FRS encapsulates the data and attributes that are associated with a replicated file (or folder) object in a staging file. The FRS needs enough staging area space on both upstream and downstream computers to replicate files.

For Windows 2000 Service Pack 2 (SP2) and later, when a staging file has been generated on the originating computer, the FRS compresses the file. This saves space in the staging file and causes less data to be replicated between members. It also makes sure that the file data can be supplied to partners no matter what file activity might prevent access to the original file.

The staging area size limits in Windows 2000 and Microsoft Windows Server 2003 are:
Default size: 660 megabytes (MB)
Minimum size: 10 MB
Maximum size: 2 terabytes
For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
221111 Description of FRS Entries in the Registry
264822 File Replication Service Stops Responding When Staging Area Is Full
If you are using Windows 2000 SP2 or earlier, note that the FRS stops replicating if the staging area runs out of free space. If a replica set member goes offline for an extended time, replication is not blocked on an upstream member because the staging area is filled. Therefore, it is a good idea to use a generous estimate for the staging area size.

Windows 2000 Service Pack 3 (SP3) and later uses an updated staging-file-management algorithm. With the updated algorithm, if the FRS tries to allocate space for a staging file but is not successful (because there is not enough space or because the space in use has reached 90 percent of the staging space limit), the FRS starts to delete staging files. Staged files are deleted (in the order of the longest time since the last access) until the space in use has dropped below 60 percent of the staging space limit. Therefore, it is not as important to use as large an estimate for the staging area size as it is for pre-SP3 systems, but it is still a good idea to do so. This helps to prevent disk or CPU resources from being consumed by repeatedly staging and deleting files.

Also, if you do not allocate enough staging area space and the service starts the cleanup process when 90 percent of the allocated space is in use, the system must generate those files again. Replication may slow down or stop if many files or very large files are moved.

Staging Size Recommendations for the FRS on Windows 2000 SP3 and Later

This tables lists recommended staging area sizes.
ScenarioMinimalAverage CaseBest Performance
Base staging space660 MB660 MB660 MB
VVJOIN (When you are adding a new member)MAX [660 MB ((128 largest files in the replica set) * number of downstream connections) * 1.2]MAX [660 MB ((128 largest files in the replica set) * number of downstream connections) * 1.2]MAX [660 MB, ((128 largest files in the replica set) * number of downstream connections) * 1.2]
Backlog (accounting for schedules)0ADDITIONAL: (Maximum expected file change quantity in a 7-day period) * 1.2ADDITIONAL: (Additional space equal to full expected replica set size) * 1.2
Configuration notesNoneDifferent drive for the staging areaDifferent drive for the staging area
RecommendationNot recommendedRecommendedRecommended for configurations with the best performance requirements
Note Use the numbers in this table as base recommendations; adjusted the values to fit your configuration.

Note that the FRS outbound log processing has been changed in the Windows 2000 post-SP2 hotfix and in SP3 to retain change orders even after they have been sent to all current downstream partners. This change permits the FRS to synchronize with a new downstream partner from the outbound log and to avoid a full IDTable scan. This change is helpful in environments where the topology changes frequently. This change is also helpful during a rollout when new members are coming online in a short time.

The default outlog change-order retention period is 7 days. The space depends on your usage and environment. Because a cleanup routine has been added that begins when 90 percent of the allocated staging space is reached, a safety factor of 1.2 has been added in the equation.

For additional information about staging area management, click the following article number to view the article in the Microsoft Knowledge Base:
321557 Improvements in the Post-S Release of Ntfrs.exe That Is Packaged with an Updated Ntfs.sys Driver

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