Sizing Journal Volumes; Determine The Required Journal Volume Capacity - HP StorageWorks P9000 User Manual

To measure write-workload and IOPS
1. Using your performance monitoring software, collect the following:
Disk-write bytes-per-second (MB/s) for every physical volume that will be replicated.
Data should be collected over a 3 or 4 week period to cover a normal, full business cycle.
Data should be collected at 5 minute intervals. If you use averages, shorter intervals
provide more accuracy.
2. At the end of the collection period, convert the data to MB, if needed, and import into a
spreadsheet tool.

Sizing journal volumes

Determine the required journal volume capacity

The following factors determine the required journal volume capacity:
The period of time during which data transfer can continue between hosts and the primary
storage system when a temporary increase in transferred data occurs or when a communication
path failure occurs between the primary and secondary storage system.
The data transfer speed for the period of time mentioned above.
To determine the journal volume capacity, use the following formula:
Formula 1 : Journal volume capacity > (V
where:
H-M
is the data transfer speed between hosts and the primary storage system.
V
M-R
is the data transfer speed between the primary storage system and the secondary storage
V
system.
t is the length of time during which data transfer can continue.
To calculate journal volume capacity that is required when a communication path failure occurs
between the primary storage system and the secondary storage system, assign zero (0) to V
The total capacity of journal volumes in each journal group must exceed the value illustrated in
formula 1.
When the data in the primary data volume of the Continuous Access Journal Z delta resync pair
is updated, if the journal data that exceeds 70 percent of the journal volume capacity on the
primary site of the Continuous Access Journal Z delta resync pair is generated, the delta resync
operation will fail. Therefore, adopt the larger value for the journal volume capacity on the primary
site of the Continuous Access Journal Z delta resync pair by comparing the values of formula 1
and formula 2.
Formula 2 : Journal volume capacity > (V × t) × 1.5
H-M M-R
- V ) × t
M-R
.
Sizing journal volumes 25