Hitachi AMS 2000 User Manual page 34

For another perspective, you can graph the data, as shown in
Figure
•
Figure 2-3: 60-Minute Rolling Averages Graphed Over Raw Data
2. From the spreadsheet or graph, locate the largest value in the E column.
This is your Peak Rolling Average (PRA) value. Use the PRA to calculate
the cumulative peak data change over cycle time. The following formula
calculates the largest expected data change over the cycle time. This will
ensure that you do not overflow your data pool.
(PRA in MB/sec) x (cycle time seconds) = (Cumulative peak data
change)
For example, if the PRA is 3 MB/sec, and the cycle time is 3600 seconds
(1 hour), then:
3MB/sec x 3600 seconds = 10,800 MB
This shows the maximum amount of changed data (pool data) that you
can expect in a 60 minute time period. This is the base data pool size
required for TCE.
3. Hitachi recommends a 20-percent safety factor for data pools. Calculate
a safety factor with the following formula:
(Combined base data pool size) x 1.2. For example:
529,200 MB x 1.2 = 635,040 MB
2–6
Hitachi AMS 2000 Family TrueCopy Extended Distance User Guide
2-3.
Plan and design — sizing data pools and bandwidth