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Guidelines for managing storage efficiency for SnapVault backups

If both the primary and secondary volumes in a SnapVault relationship have storage efficiency enabled, then data transfers to the SnapVault secondary volume preserve storage efficiency. If the primary volume does not have storage efficiency enabled, you might want to enable storage efficiency only on the secondary volume.

Because SnapVault secondary volumes typically contain a large amount of data, storage efficiency on SnapVault secondary volumes can be very important.

If storage efficiency is enabled on the primary volumes

If the primary volume in a SnapVault relationship is enabled for storage efficiency, all data backup operations preserve the storage efficiency.

If storage efficiency is enabled only on the secondary volume

If the primary volume in a SnapVault relationship does not have storage efficiency enabled, you might want to enable storage efficiency for the secondary volume because it is likely to contain a large amount of data over time.

You can use the volume efficiency command to start a scan on the volume if there is already data on the volume from transfers. If this is a new relationship with no transfers, then there is no need to run the scan manually.

Changes to the volume's efficiency schedule do not take effect for a SnapVault secondary volume. Instead, when storage efficiency is enabled, the SnapVault relationship manages the schedule. When a data transfer begins, the storage efficiency process automatically pauses until the transfer is finished, and then automatically begins again after the data transfer is complete. Because data transfers to a SnapVault secondary volume might include more than one Snapshot copy, the storage efficiency process is paused for the entire duration of the update operation. After the transfer is finished and the post-transfer storage efficiency process is complete, the last Snapshot copy created in the secondary volume is replaced by a new, storage-efficient Snapshot copy.

If the last Snapshot copy that is created in the secondary volume is locked before it can be replaced by a new, storage-efficient Snapshot copy, then a new, storage-efficient Snapshot copy is still created, but the locked Snapshot copy is not deleted. That Snapshot copy is deleted later during the storage-efficient cleanup process after a subsequent update to the SnapVault secondary volume and after the lock is released. A Snapshot copy in a SnapVault secondary volume might be locked because the volume is the source in another relationship, such as a data protection mirror relationship.

If the secondary volume has additional compression enabled, storage efficiency is not preserved

Storage efficiency on all data transfers in SnapVault relationships is not preserved when the secondary volume has additional compression enabled. Because of the loss of storage efficiency, a warning message is displayed when you enable compression on a SnapVault secondary volume. After you enable compression on the secondary volume, data transfers are no longer storage efficient. You can reenable storage efficiency on data transfers after you disable compression on the secondary volume.