Software Owner manual

Figure 1 Snapshot XP mechanism

In Figure 1, Data A is stored in the Snapshot XP pair's P-VOL. When the host requests to update Data A

to Data B, S n apshot XP copies Data A to the pool volume (pool-VOL) in the pool before updating the

P-VOL. After the copy operation for Data A is complete, Snapshot XP writes Data B to the area where

Data A was stored in the P-VOL, and the P-VOL is updated. From the S-VOL, you can acc ess Data B in the

P-VOL and D ata A in the pool-VOL.

Snapshot XP and Business Copy XP are similar because both create pairs. However, Snapshot XP pair

S-VOLs do not consume array capacity because the S-VO L s are actually virtual volumes. Therefore,

Snapshot XP reduces the capacity the array uses as a whole.

The copy process for Business Copy XP pairs takes longer because all P-VO L data is copie d to the S-VOL.

On the other hand, the copy process for Snapshot XP pairs takes less time c ompared to the copy process

for Business Copy XP pairs because, as you can see in Figure 1, only updated P-VOL data is copied to

the pool-VO L. The same data in the P-VOL can be referenced by accessing the Snapshot XP pair's S-VOL,

but the actual data does not exist in the S-VOL. The P-VOL data can be referenced using the S-VOL.

As described previously, Snapshot XP requires less capacity in the array and less copy processing time

compared to Business Copy XP. HP recommends using Snapshot XP to copy and manage data in the

short term with reduced costs. H owever, Snapshot XP only copies some of the P-VOL data. Therefore,

data stored in the S-VOL is not gua ranteed in the following:

• WhenaphysicalfailureoccursinaP-VOL

• When a pool is blocked

On the other hand, Business Copy XP copies all P-VOL data to the S-VOL. Therefore, even if a physical

failure occurs in a P-VOL, you can recover the P-VOL data using the S-VOL data. Business Copy XP

provides higher integrit y than Snapshot XP. HP recommends using Business Copy XP when data integrity

is more important than copy process speed or array capacity. For a functional overview of Business

Copy XP, see Business Copy XP.

Overview of copy solutions