When updating the primary volume, Thin Image stores the differential data in a Thin Image pool or an HDP pool as snapshot data. If a failure occurs in the data in the storage system, the data can be restored by using the snapshot data. A REST API client issues an API to perform operations for Thin Image.
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When a Thin Image pair without a secondary volume is created:
If a problem occurs in the primary volume data, the primary volume can be restored by using the snapshot data. A secondary volume can be allocated later to the snapshot data when the secondary volume becomes necessary.
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When a Thin Image pair with a secondary volume is created:
The primary volume can be restored by using the snapshot data. In addition, a copy of the primary volume from when the snapshot data was stored can be viewed from the secondary volume. The following figure shows an example of obtaining a snapshot of a Thin Image pair.
To store snapshot data, create a Thin Image pair where an LDEV or a DP volume is used as a primary volume, and a virtual volume for Thin Image or a DP volume is used as a secondary volume. If the created pair is registered to a snapshot group or a consistency group, processing can be performed by group. If a consistency group is defined, the snapshot data from when the storage system received a request can be stored for all the primary volumes in that consistency group.
You can create a cascade configuration by creating a Thin Image pair for another Thin Image pair. You can also create a clone of a Thin Image pair and use the created clone as DP volumes.
For details about Thin Image, see the Hitachi Thin Image User Guide.