HP StorageWorks XP Remote Web Console Software - Manual (Page 10)

In Figure 2 (page 9) , Data A is stored in some part of the P-VOL of an XP Snapshot pair. When
the host requests an update of Data A to Data B, XP Snapshot will copy Data A to the pool volume
in the pool before the P-VOL is updated. After the copy operation of Data A has completed, Data
B will be written to the part where Data A was stored in P-VOL, and the P-VOL will be updated.
From the V-VOL, you can access Data B in the P-VOL and Data A in the pool-VOL.
Create V-VOL Management Area Operation
A V-VOL management area needs to be created in the shared memory before you use XP Snapshot.
The V-VOL management area is an important area for associating an S-VOL (a V-VOL) of XP
Snapshot with a pool-VOL. The V-VOL management area is created automatically when the
additional shared memory is installed. Call HP technical support for the installation of additional
shared memory.
There are two kinds of areas in the V-VOL management area: pool management block and pool
association information. When you create pools or XP Snapshot pairs, the pool management block
or pool association information will be stored in the V-VOL management area; therefore, the
available capacity of the V-VOL management area decreases. When all capacity of the V-VOL
management area is used, the capacity ratio of the pool management block and the pool association
information in the V-VOL management area will be fixed. If the capacity of the pool management
block is insufficient, problems may occur; for example, you cannot create new pools or create
pools with a large amount of capacity. To solve such problems, you need to optimize the V-VOL
management area.
Creation of a Pool
An XP Snapshot pool is an area to store snapshot data. A pool consists of multiple pool-VOLs, and
snapshot data is stored in a pool-VOL. 1024 pool-VOLs can be registered in a pool, and 128
pools can be created in a storage system.
Figure 3 (page 10) illustrates the relationship between
an XP Snapshot pair and a pool.
Figure 3 The Relationship Between an XP Snapshot Pair and a Pool
10 About XP Snapshot Operations