A snapshot or FlashCopy® is an instant, point-in-time copy of a logical unit (LUN) or a set of LUNs.
FlashCopy and Snapshots
The term FlashCopy is used for IBM® System Storage® DS8000®, IBM System Storage SAN Volume Controller, and IBM Storwize® V7000 storage devices. A FlashCopy creates a point-in-time copy in which the target volume represents an exact copy of the data on a source volume at the time the FlashCopy was started. Data that existed on the target volume is replaced by the copied data. When you perform a FlashCopy of a source volume, Tivoli® Storage FlashCopy Manager requires that the target volume must be the same size as the source volume. In addition, the target volume and source volume must have the same logical track format. The source and target volumes must also be on the same storage system.
For IBM XIV® Storage System, IBM System Storage N series, NetApp, and file systems such as GPFS™, the term snapshot is used. A snapshot represents a point-in-time copy of a volume or set of volumes without having to define a specific target volume. The source volumes and snapshots are located on the same storage system. Similarly, a file system snapshot represents a point-in-time copy of a file system or file set within a file system. The space that is required for the snapshot is allocated automatically within the same storage system or file system and can increase over time.
Using a FlashCopy or snapshot you can back up data from source volumes to target volumes. Similarly, you can back up file systems or file sets within a file system. When data is restored, backup copies are retrieved and the data is copied to the source volume or copied to the original location in the file system or file set.
Types of snapshot backups
There are two types of snapshot backups, a full copy snapshot or a space-efficient snapshot. The type of snapshot backups that are available are dependent on the storage environment. During a full copy snapshot, all blocks of data on the source volume are copied to the target volume. During a space efficient snapshot, only those blocks of data that are overwritten on the source volume are copied.
Transferring snapshots to Tivoli Storage Manager
In addition, when you use Tivoli Storage FlashCopy Manager with Tivoli Storage Manager products, you can transfer snapshots to Tivoli Storage Manager. To send these snapshot backups to Tivoli Storage Manager, you must configure a backup server or cluster.
