Hitachi Thin Image stores snapshots in a Hitachi Virtual Storage Platform family (VSP family) storage system. If the data of the storage system fails, you can restore it using the stored snapshot of the data. Pairs created by using Thin Image are called Thin Image pairs in this document.
To store snapshot data, you create a pair with a logical volume functioning as the P-VOL, and a virtual volume as the S-VOL. A pair created to store snapshot data is referred to as a snapshot pair. A snapshot pair displays showing the snapshot attribute.
When you create a Thin Image pair, the status changes to "PAIR" and snapshot data is stored. You can use Thin Image to store a maximum of 1,024 snapshots of data (including the number of clones when you clone a volume).
Updating the P-VOL first copies the differential data as snapshot data in pool volumes (pool-VOL), and then updates the data. Snapshot data is a copy of differential data in Thin Image P-VOLs. If your storage system experiences a data storage failure, you can restore the data using the snapshot data in the pool.
Splitting a Thin Image pair saves a snapshot and stops the copying of replaced data in the pool.
The following figure provides a basic illustration of storing snapshot data.
You can use snapshot data in open-system volumes.