Establishing Data Pool Size; Measuring Workload Data, Sizing The Data Pool - Hitachi AMS2100 User Manual

Establishing data pool size

Measuring workload data, sizing the data pool

Hitachi AMS 2000 Family Copy-on-Write SnapShot User Guide
The data pool holds data from the P-VOL that is being replaced. By
holding this original data in the data pool, the mirror image of the P-
VOL at the time of the snapshot is maintained.
You determine the size of the data pool that your system requires by:
• Measuring the amount of write workload that passes from the
host application to the P-VOL. Write workload is the megabytes
per second that are written to the primary volume over a specific
time.
• Calculating the amount of data that would accumulate during
the lifespan of your V-VOL.
• Multiplying the amount of data that accumulates by the number
of V-VOLs.
•
Figure 2-2: Write workload and data pool size
To set up SnapShot, you must measure the amount of data that
changes in your production system. The amount of data written to
the primary volume indicates how large the data pool must be.
Workload data is collected using performance monitoring software on
your operating system—preferably during the busiest time of month,
quarter, and year. The goal is to collect data that shows your system's
actual workloads during high peaks and spikes, when more is
changing and the demands on the system are greatest.
To collect workload data and size the data pool
1. Using your operating system's performance monitoring software,
collect the following:
- Disk-write bytes/second for every physical volume that will
be replicated.
- Collect this data at 10 minute intervals.
Planning and design
2-5