Dell PowerVault NX1950 - Manual (Page 16)

16 Deployment Guide
For example, you can query all documents containing the word product or you
can query for all Microsoft Office documents written by a specific author. The
Indexing service returns a list of all documents that meet your search criteria.
NOTE: Indexing is not supported in clustered environments.
Single Instance Storage
SIS recovers disk space by reducing the amount of redundant data stored in a
volume. To recover the disk space, SIS performs the following procedures:
• Identifies identical files
• Stores one copy of the file in the SIS common store
• Replaces the files with pointers to the file in the SIS common store
For example, User A and User B receive the same e-mail with an attachment.
Both users save the attachment to their home folder. SIS detects the two
identical files on the volume, moves one of the copies into the SIS common
store, and then replaces both files with a pointer to the file in the SIS
common store.
Subsequently, User A makes a change to the file. SIS immediately detects that
an update is pending for the file, removes the pointer in the user’s home folder,
and replaces the pointer with a copy of the file in the SIS common store.
The updates are then applied to a fresh copy of the original file. This process
is completely transparent to the application.
The User B file remains in the SIS common store with a pointer in the User B's
home folder, even if there is only one pointer to the file. When User B updates
the file (assuming there are no other pointers), the pointer is deleted and
replaced with a copy of the original file. The file in the SIS common store is
then deleted.
SIS works in the background and does not require user intervention.
The administrator can enable SIS on a per-volume basis. For best results, the
administrator should use a backup application that supports SIS.