Single Instance Storage Volume Support (4036234)

This article discusses the affects of enabling the Single Instance Storage feature for the volumes where the AppAssure repositories are stored.

The Single Instance Storage (SIS) feature reduces the amount of space that is used to store data on a volume. SIS does this by replacing duplicate files with logical links that point to a single copy of the file in the SIS Common Store, which is a hidden folder that is located in the root directory of the volume.

Backup and recovery by using SIS should have the following requirements:

• The backup software used must support SIS-enabled volumes.
• The SIS volume, SIS Common Store folder, and reparse points (links) to the files must be restored to a Windows 2000 NTFS version 5.0 (or later) file system or partition that supports reparse points or junction points.
• The Single Instance Storage Filter must be installed or enabled to access the data in the SIS volume.
• The backup program must be capable and configured to backup and restore the reparse points or junction points (links) to the files, and the SIS volume and the SIS Common Store folder must be selected.

Microsoft has released a list of known issues regarding SIS enabled volumes on Windows 2008 Storage.
http://technet.microsoft.com/en-us/library/dd904408%28WS.10%29.aspx -

Single Instance Storage (SIS) is similar to deduplication. An AppAssure repository cannot be stored on a deduped or compressed volume, as AppAssure has it’s own compression and deduplication methods built in.

Any volume where the AppAssure repository is stored should not have SIS enabled. It provides no added benefit, while presenting a high risk when multiple extents to a repository are added, or when multiple repository files have the same names and sizes.