HP StorageWorks XP Remote Web Console Software - Manual (Page 23)

NOTE:
You can check the capacity of the shared memory of pool association information and pool
management block in the XP Snapshot pane.
For details of the shared memory capacity for the whole V-VOL management area, see
Table
5 on page 21.
To calculate S2 (Shared memory capacity for pool management block), use the formula below:
S2 = {( Y / 256) x (32 / 74784)} x 74784
Y — Total capacity of the pool-VOLs (in kilobytes) 256: Capacity of one slot (in kilobytes)
32 — Capacity of the table which you need to manage the pool of one slot 74784: Minimum size
of pool management block.
NOTE:
You must round up the value enclosed by two upward arrows ( ) to the nearest whole number.
NOTE:
•
You can check the shared memory capacity of the pool association information and pool manage-
ment block in the XP Snapshot pane (
Figure 18 on page 67).
NOTE:
When calculating a pool's usage:
• When copying snapshot data to the pool, XP Snapshot always uses a multiple of 256 KB of the
pool's capacity, even when the snapshot data is smaller than 256 KB.
• When snapshot data is stored consecutively, snapshot data capacity and pool usage is almost
the same. However, pool usage will be larger than snapshot data capacity when snapshot data
is stored randomly.
When the shared memory capacity for the whole V-VOL management area (“S” in the formula above)
is 1,024 MB, the capacity of the pool-VOL (“Y” in the formula above) is 4 TB (4,398,046,511,104
kB), and the capacity of one P-VOL is 10 GB, the number of XP Snapshot pairs that can be created
for a subsystem can be calculated as follows.
XP Snapshot User Guide 23