IBM DS8000 manual 175, CKD RAID rank capacity

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.

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

	Spare /		Binary	Decimal	3390-3	3390-9	32760 cyl	65520 cyl
Rank	No spare	Extents	GB	GB	devices	devices	devices	devices
RAID10 73GB	Spare	216	190.30	204.34	72	24	7	3
RAID10 73GB	No spare	288	253.74	272.45	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

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.

Figure 9-7 CKD RAID rank capacity

Chapter 9. Configuration planning 175