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Chapter 9. Configuration planning 175
DS8000 adopts a virtualization concept, which was introduced in Chapter 5, “Virtualization
concepts” on page 83.
The logical capacity depends on the RAID type and the number of spare disks in a rank. We
explain the capacity with the following figures.
Figure 9-7 CKD RAID rank capacity
Attention:
The figures used in this section are still subject to change. Specifically, the exact
number of extents per array may be slightly different.
Generally speaking, you might ensure there is at least 5% of additional capacity if you
are providing an exact number of devices.
– There will also potentially be unusable space for devices which are not an integer
number of extents in size and for the last extent in an extent pool.
– To prepare for the unexpected situation, a certain amount of margin is required for
important systems.
Note: IBM will offer Capacity Magic for the DS8000 in the future. Capacity Magic
calculates the physical and effective storage capacity of a DS8000. IBM engineers and
IBM Business Partners can download this tool from an IBM Web site. The following figures
are intended to be used only until Capacity Magic is available.
CKD RAID rank capacity
Notes
There may be space left over when defining the devices shown in the table.
Devices that are not a multiple of 1113 cylinders will use additional space on the disk
subsystem as the allocation unit is an extent of this size.
Rank
Spare /
No spare Extents
Binary
GB
Decimal
GB
3390-3
devices
3390-9
devices
32760 cyl
devices
65520 cyl
devices
RAID10 73GB Spare
216190.30204.34 72 24 7 3
RAID10 73GB No spare
288253.74272.45 96 32 9 4
RAID10 146GB Spare
435 383.25 411.51 145 48 15 7
RAID10 146GB No spare
581 511.88 549.63 193 64 20 10
RAID10 300GB Spare
883 777.96 835.32 294 98 30 15
RAID10 300GB No spare
1,178 1,037.86 1,114.39 392 130 40 20
RAID5 73GB Spare
434 382.37 410.57 144 48 14 7
RAID5 73GB No spare
507 446.69 479.62 169 56 17 8
RAID5 146GB Spare
873 769.14 825.86 291 97 30 15
RAID5 146GB No spare
1,018 896.89 963.03 339 113 35 17
RAID5 300GB Spare
1,771 1,560.32 1,675.38 590 196 61 30
RAID5 300GB No spare
2,066 1,820.22 1,954.45 688 229 71 35