HP StorageWorks XP Remote Web Console Software - Manual (Page 22)

22 Requirements for Snapshot XP operations
Uninstalling Snapshot XP
1. Delete all Snapshot XP pairs.
2. Delete all pools.
3. Delete all V-VOLs.
4. Uninstall Snapshot XP.
For more information about deleting pairs, pools, and V-VOLs, see ” Snapshot XP operations ” on
page 37.
Calculating the number of Snapshot XP pairs you can create
The number of Snapshot XP pairs you can create for an array depends on the number of differential
tables, V-VOL management area’s shared memory capacity, or number of pair tables. To calculate the
number of Snapshot XP pairs you can create, first use the number of differential tables, then use the V-VOL
management area’s shared memory capacity, and finally use the number of pair tables. Then compare
the three results. The smallest value is the maximum number of Snapshot XP pairs you can create for the
array.
Using the number of differential tables
You can use a maximum of 13,652 differential tables for an array if additional shared memory is not
installed. You can use a maximum of 30,718 differential tables if additional shared memory is installed.
To calculate the number of Snapshot XP pairs you can create, calculate the number of differential tables
required for the Snapshot XP pair and compare it with the number of differential tables for the whole
array. In addition to Snapshot XP, the following software products use differential tables in the array:
• Business Copy XP
• ShadowImage for z/OS
• Hitachi FlashCopy Mirroring
• Hitachi FlashCopy Mirroring Version 2
• Flex Copy XP
• Auto LUN XP
If you use any of these software products in the same array, calculate the number of differential tables
Snapshot XP pairs can use by subtracting the number of differential tables the pairs use (migration plan
for Auto LUN XP) for these software products from the number of differential tables for the whole array.
For more information about calculating the number of required differential tables for Business Copy XP,
ShadowImage for z/OS, Hitachi FlashCopy Mirroring, Hitachi FlashCopy Mirroring Version 2, Flex
Copy XP, and Auto LUN XP, see the software product’s manual.
To calculate the number of differential tables for each Snapshot XP pair, use the following formula:
( (X) ч 256) ч (Z)
where:
(X) is the volume’s capacity (in kilobytes)
(Z) is the number of slots a differential table can manage (1,916 × 32)
You must round up the calculation result to the nearest whole number.
If the volume’s capacity ((X) in the previous formula) is 16 GB (16,777,216 KB), the number of differential
tables for each Snapshot XP pair is calculated as:
(16,777,216 ч 256) ч (1,916 Ч 32) = 1.06889
Round up 1.06889 to 2. Therefore, two differential tables are required to create a Snapshot XP pair.
Assume that no other software products use differential tables in an array where additional shared
memory is not installed. The number of differential tables that Snapshot XP can use is 13,652. To create
Snapshot pairs that require two differential tables for each pair, the calculation is as follows:
13,652 ч 2 = 6,826