Hitachi MK-97DF8018-00 Computer Drive User Manual


 
2–4 Planning and Design
Hitachi Simple Modular Storage Copy-on-Write SnapShot User’s Guide
If the snapshot is to be used as a disk-based backup available for online
recovery, you can determine the lifespan by multiplying the number of
generations of backup you want to keep online by the snapshot
frequency. For example:
Generations held = 4
Snapshot frequency = 4 hours
4 x 4 = 16 hours
V-VOL lifespan = 16 hours
Lifespan Based on Business Uses
If you use snapshot data (the V-VOL) for testing an application, the
testing requirements determine the amount of time a snapshot is held.
If snapshot data is used for development purposes, development
requirements may determine the time the snapshot is held.
If snapshot data is used for business reports, the reporting
requirements can determine the backup’s lifespan.
Establishing the Number of V-VOLs that Are Required
V-VOL frequency and lifespan determine the number of V-VOLs your system
needs per P-VOL.
For example: Suppose your data must be backed up every 12 hours, and
business-use of the data in the V-VOL requires holding it for 48 hours. In
this case, your SnapShot system would require 4 V-VOLs, since there are
four 12-hour intervals during the 48-hour period. This is illustrated in
Figure 2-1.
Figure 2-1: V-VOL Frequency, Lifespan