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Appendix E Logical Disk Used Capacity
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(3) List of samples
(4) Supplementary explanation
For the capacity of logical disks you can bind in unused space, it depends on how many logical
disks are in the pool.
For example, when you bind 127 logical disks and if there is a pool whose unused space is 2.0 GB,
you can locate one 2.0-GB logical disk in the pool, but you cannot locate two 1.0-GB logical
disks; because the control region already assigned is used for the 128 logical disks, but a 256-MB
new control region is required for 129-th and later logical disks.
2. Basic pool
A basic pool consists of multiple partitions in a RAID configuration, and the partitions are
assigned by units of 1 MB. Therefore, because the partitions need to be equally used on area
assignment to logical disks, the capacity occupied is a multiple of the number of partitions
multiplied by 1 MB.
RAID1 - 1 partition
RAID5 - 1 partition
RAID10 (4 PDs) - 2 partitions
RAID10 (8 PDs) - 4 partitions
RAID10 (16 PDs) - 8 partitions
RAID50 (10 PDs) - 2 partitions
RAID50 (20 PDs) - 4 partitions
(1) Formula
Use the following formula to calculate the pool used capacity when the logical disk capacity (user
available capacity) required is X (MB) and the number of RAID partitions is N:
Y = (X + 2) mod N
When Y = 0,
Pool used capacity = X + 2
No. of Logical Disks Capacity Pool Used Capacity
1 2.0 GB 2.25 GB (2.2 GB on iSM)
129 2.0 GB 258.50 GB (258.5 GB on iSM)
1 Recommended capacity 2.0 GB 2.50 GB (2.5 GB on iSM)
129 Recommended capacity 2.0 GB 290.75 GB (290.7 GB on iSM)