Hitachi AMS2100 User Manual page 60

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Hitachi AMS 2000 Family Copy-on-Write SnapShot User Guide
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Figure 2-5: Rolling Averages Graphed Over Raw Averages
4. Locate the maximum rolling average (RA) value in the C column.
Using this peak value and the following formula, calculate the
cumulative peak data change over the lifespan of a copy (V-VOL):
(RA peak MB/sec) x (V-VOL lifespan seconds) =
(Cumulative data over V-VOL lifespan)
For example, if the RA peak is 25 MB/sec, and the V-VOL lifespan
is 3600 seconds (1 hour), then:
25MB/sec x 3600 seconds = 90,000 MB
Cumulative data over a V-VOL's 1-hour lifespan is 90,000 MB.
5. Calculate the base data pool size for your primary/virtual volumes
by multiplying the MB size of one V-VOL in Step
of V-VOLs, which was established earlier. For example:
x 4 V-VOLS = 360,000 MB
90,000 MB
This is the base data pool size for a SnapShot system in which the
copy frequency is 1 hour, the copy lifespan is 4 hours, and the
number of copies (V-VOLs) is 4.
6. It is highly recommended that a safety factor of 20%, be
calculated. Do so using the following formula:
(Base data pool size) x 1.2. For example:
Planning and design
4 by the number