Single Instance Storage - Dell PowerVault NX1950 Deployment Manual

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 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.
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Deployment Guide