Best Practices for Shadow Copies of Shared Folders

Applies To: Windows Server 2008 R2, Windows Server 2012

We recommend that you consider the following best practices when you work with Shadow Copies of Shared Folders.

Use a separate volume on another disk as the storage area for shadow copies.

• Select a storage area on a disk that is not being shadow copied. Using a separate volume on another disk eliminates the possibility that high I/O load will cause shadow copies to be deleted and provides better performance. This is the recommended configuration for heavily used file servers. For failover clusters, this configuration also requires that the original volume and storage volume belong to the same cluster resource group.
  

If you are using failover clusters, two volumes on the same disk cannot be associated for diff area storage.

• This is because the cluster manages the disk for online and offline operations, but the Volume Shadow Copy Service (VSS) needs to have the diff area and original volumes brought offline or online in a specific order. Instead, the storage volume and the original volume need to be the same volume, or they need to be on separate physical disks.
  

Consider how your clients will use a shared resource before you enable Shadow Copies of Shared Folders and set scheduling options.

• Adjust the shadow copy schedule to fit the work patterns of your clients.
  

Do not enable shadow copies on volumes that use mount points.

• The mounted drive will not be included when shadow copies are created. Enable shadow copies only on volumes without mount points or when you do not want the shared resources on the mounted volume to be shadow copied. Alternatively, you can explicitly include the mounted volume in the schedule for shadow copy creation. (For previous versions of a file to be available, the volume must have a drive letter assigned.)
  

Perform regular backups of your file server.

• Shadow Copies of Shared Folders is not a replacement for performing regular backups. Use a backup utility, such as Windows Server Backup in Windows Server 2008 or Windows Server 2008 R2, in coordination with Shadow Copies of Shared Folders as your strategy for data protection.
  

Do not schedule copies to occur more often than once per hour.

• The default schedule for creating shadow copies is at 7:00 A.M., Monday through Friday. If you decide that you need copies to be created more often, verify that you have allotted enough storage space and that you do not create copies so often that server performance degrades. There is also an upper limit of 64 copies per volume that can be stored before the oldest copy is deleted. If shadow copies are created too often, this limit might be reached very quickly, and older copies could be lost at a rapid rate.
  

Before deleting a volume that is being shadow copied, delete the scheduled task for creating shadow copies.

• If the volume is deleted without deleting the shadow copy task, the scheduled task will fail and an Event ID: 7001 error will be written to the event log. Delete the task before deleting the volume to avoid filling the event log with these errors. To manually delete the scheduled task, click Start , point to Administrative Tools , and then click Task Scheduler . In Task Scheduler, click Task Scheduler Library , right-click the task to create shadow copies, and then click Delete .
  

Use an allocation unit size of 16 kilobytes (KB) or larger when formatting a source volume on which Shadow Copies of Shared Folders will be enabled.

• If you plan to defragment the source volume on which Shadow Copies of Shared Folders is enabled, we recommend that you set the cluster allocation unit size to be 16 KB or larger when you initially format the source volume. If you do not, the number of changes caused by defragmentation can cause previous versions of files to be deleted.
  
• If you require NTFS file compression on the source volume, you cannot use an allocation unit size larger than 4 KB. In this case, when you defragment a volume that is very fragmented, you may lose older shadow copies faster than expected.
  

After backing up a volume that contains shadow copies, do not restore the volume to a different volume on the same computer

After backing up a volume that contains shadow copies, do not restore the volume to a different volume on the same computer as this will leave multiple snapshots with the same Snapshot ID on the system and will cause unpredictable results when performing a shadow copy revert.
You can restore the volume to the original volume on the same computer; you can restore the volume to a different volume on a different computer, or you can restore file and folders to any location on the same computer.

Additional references

• Enable and Configure Shadow Copies of Shared Folders
  
  
• Shadow Copies of Shared Folders
  
  
• Troubleshooting Shadow Copies of Shared Folders