HP XP RAID Manager Software - Manual (Page 17)

The following table shows a system’s shared memory capacity based on the amount of additional
shared memory. This table also shows the V-VOL management area’s memory capacity.
Shared memory capacity Shared memory
751,619,276 bytes SS
4,294,967,296 bytes SS Extension 1
You can calculate the maximum number of SS pairs that you can create based on the amount of
additional shared memory in the V-VOL management area.
Use the following workflow to calculate the maximum number of pairs:
1. Calculate the capacity of the pool management block, which is the total capacity of shared
memory used by the pool-VOL (see
(page 18) ).
2. Calculate the capacity of pool association information, which is the total capacity of shared
memory used by the P-VOL (see
(page 18) ).
NOTE: ceil in the formulas indicates that you must round up the result within the parenthesis ()
that follows.
floor in the formulas indicates that you must round down the result within the parenthesis () that
follows.
Example
This example assumes the following:
•
The V-VOL management area’s shared memory has a capacity of 716 MB (751,619,276
bytes).
•
There are four pool-VOL pools, each having a capacity of 1 TB (1,073,741,824 KB).
•
Each P-VOL has a capacity of 10 GB (10,485,760 KB).
Use the following formula to calculate the maximum number of SS pairs (P-VOLs) you can create
in a storage system:
The capacity (bytes) of shared memory used by the pool-VOL =
ceil (floor (1,073,741,824 (KB)/256 (KB)) X 32/8,640) X 8,736 +
ceil (ceil (floor (1,073,741,824 (KB)/256 (KB)) X 32/8,640) X 8,736 +
ceil (ceil (ceil (floor (1,073,741,824 (KB)/256 (KB)) X 32/8,640) X 8,736
= 135,713,760 + 69,888 + 8,736
= 135,792,384 (bytes)
The capacity of the pool management block = 135,792,384 X 4
= 543,169,536 bytes
The capacity (bytes) of shared memory used by the P-VOL =
ceil (ceil (10,485,760 (KB)/256 (KB))/2,048) X 8,736 +
ceil (ceil (ceil (10,485,760 (KB)/256 (KB))/2,048) X 8,736
= 17,472 +8,736
= 26,208 (bytes)
Maximum number of SS pairs (P-VOLs) = (751,619,276 - 543,169,536) / 183,456
= 208,449,740 / 183,456
= 1,136
Using these examples, the maximum number supported based on additional shared memory in
the V-VOL management area is 1,136 pairs.
Calculating the number of Snapshot pairs 17