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Appendix E Logical Disk Used Capacity
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Appendix E Logical Disk Used Capacity
The list below shows the difference between the pool used capacity and the logical disk capacity on the
100/1000/2000 series disk array (not including S400/S1400/S2400):
The relation (formula for calculating the relation) between the pool used capacity and the associated logical disk
capacity depends on the pool type:
1. Dynamic pool
The minimum unit of assigning an area in a dynamic pool is 256 MB, and the 2-MB control
region is secured in another place. Therefore, when the number of disks is 128 or less, the
amount of the control region secured in the pool is 256 MB, and when the number of disks is
between 129 and 256, it is 512 MB.
(1) Formula
Use the following formula to calculate the pool used capacity when the capacity of logical disks
(user available capacity) required is X (MB) and the number of logical disks is Y:
Pool used capacity = ([(X - 1)/256] + 1) × 256 × Y + ([(Y - 1)/128] + 1) × 256
(X,Y > 0)
[X] is a gaussian which represents an integer below X.
(2) Examples
When you bind one 2.0-GB logical disk, the pool used capacity required is:
([(2048 - 1)/256] + 1) × 256 × 1 + ([(1 - 1)/128] + 1) × 256 = 2048 + 256 = 2304 MB
When you bind one logical disk with the recommended capacity 2.0 GB, the pool used capacity
required is:
([(2126 - 1)/256] + 1) × 256 × 1 + ([(1 - 1)/128] + 1) × 256 = 2304 + 256 = 2560 MB
Disk Array Series Name Logical Disk Capacity Pool/RANK Used Capacity
100/1000/2000
User available capacity + 2 MB + α
Equal to disk capacity
400/1400/2400/2800 User available capacity + 2 MB
Specified capacity + 2 MB + α