HP 2000i HP StorageWorks 2000 G2 Modular Smart Array reference guide (500911-0 - Page 21
About the Volume Copy feature, existed when a specified snapshot was created preserved
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The snapshot service has two features for reverting data back to original data: • Deleting only modified data on a snapshot. For snapshots that have been made accessible as read-write, you can delete just the modified (write) data that was written directly to a snapshot. When the modified data is deleted, the snapshot data reverts to the original data that was snapped. This feature is useful for testing an application, for example. You might want to test some code, which writes data to the snapshot. Rather than having to take another snapshot, you can just delete any write data and start again. • Rolling back the data in a source volume. The rollback feature enables you to revert the data in a source volume to the data that existed when a specified snapshot was created (preserved data). Alternatively, the rollback can include data that has been modified (write data) on the snapshot since the snapshot was taken. For example, you might want to take a snapshot, mount that snapshot for read/write, and then install new software on that snapshot for test purposes. If the software installation is successful, you can rollback the master volume to the contents of the modified snapshot (preserved data plus the write data). The following figure shows the difference between rolling back the master volume to the data that existed when a specified snapshot was created (preserved), and rolling back preserved and modified data. MasterVolume-1 Snapshot-1 Preserved Data (Monday) Modified Data (Tuesday) When you use the rollback feature, you can choose to exclude the modified data, which will revert the data on the master volume to the preserved data when the snapshot was taken. Snap Pool-1 MasterVolume-1 Snapshot-1 Preserved Data (Monday) Modified Data (Tuesday) Or you can choose to include the modified data since the snapshot was taken, which will revert the data on the master volume to the current snapshot. Snap Pool-1 Figure 2 Rolling back a master volume About the Volume Copy feature Volume Copy is a licensed feature that enables you to copy a volume or a snapshot to a new standard volume. While a snapshot is a point-in-time logical copy of a volume, the volume copy service creates a complete "physical" copy of a volume within a storage system. It is an exact copy of a source volume as it existed at the time the volume copy operation was initiated, consumes the same amount of space as the source volume, and is independent from an I/O perspective. Volume independence is a key distinction of a volume copy (versus a snapshot, which is a "virtual" copy and dependent on the source volume). HP StorageWorks 2000 G2 Modular Smart Array Reference Guide 21