Single instance storage of the archived items lets Backup Exec identify the shareable parts of an item. An example of a shareable part is a message attachment or the contents of a document. Backup Exec then stores the parts separately, and only once. When Backup Exec identifies a shareable part that is already stored in a vault store, it references the stored shareable part instead of archiving it again.
If single instance storage is enabled. items are shared within and across vault stores and vault store partitions. The vault store partitions may be on different device types. Shareable parts of a message that exceed the single-instance threshold of 20 KB are shared. These parts include attachments and message bodies. The user information and the shareable parts that are under the single instance storage threshold are not shared.
Enabling this option can provide a significant reduction in the storage space that is required for archived items. If you enable single instance storage, you should back up the fingerprint databases. Single instance storage-related information is contained in the fingerprint databases for all of the vault stores.