A LUN clone is a space-efficient copy of another LUN. Initially, the LUN clone and its parent share the same storage space. More storage space is consumed only when one LUN or the other changes.
In releases prior to Data ONTAP
7.3, SnapVault considers each LUN clone as a new LUN. So, during the initial transfer of the LUN clone, all data from the clone and the backing LUN is transferred to the secondary storage system.
For descriptions of data backup and restore on volumes containing LUNs, see the Data ONTAP Block Access Management Guide for iSCSI and FC.
Starting with
Data ONTAP 7.3,
SnapVault can transfer LUN clones in an optimized way by using
SnapDrive for Windows. To manage this process,
SnapDrive for Windows
creates two
Snapshot copies:
- Backing Snapshot copy, which contains the LUN to be cloned
- Backup Snapshot copy, which contains both the LUN and the clone
Modes of transfer
Starting in
Data ONTAP 7.3, a
SnapVault transfer with LUN clones can run in two modes:
- In non-optimized mode, a LUN clone is replicated as a LUN. Therefore, a LUN clone and its backing LUN get replicated as two separate LUNs on the destination. SnapVault does not preserve space savings that come from LUN clones.
- In optimized mode, a LUN clone is replicated as a LUN clone on the destination. Transfers of LUN clones to the secondary storage system in optimized mode are possible only with SnapDrive for Windows.
These modes apply to newly created LUN clones. On successive update transfers, only the incremental changes are transferred to the destination in both modes.
Note: A single relationship must either be optimized or non-optimized. Switching between the two modes is not allowed.
