Appendix C. Solid State Drives on the IBM System Storage DS5000 series 531
Identifying SSD in Storage Manager
You can identify SSDs in Storage Manager either by the label “SSD” or an icon, as shown in
Figure C-3, in the row “Media Type”.
Figure C-3 SSD properties
SSD arrays
The same criteria for arrays apply to SSD as for other type disk drives. All of the disk drives in
the SSD array must have the same media type (SSD) and the same interface type (FC only).
Hot spare disk drives must also be SSD and be the same type as the disk drives they are
protecting.
Wear life
The flash-based SSD has a limited wear life before individual memory locations can no longer
reliably store data. The disk drive continuously monitors itself and reports its wear life status
to the controller. Two mechanisms exist to alert you that an SSD is nearing the end of its
useful life:
Average erase count
Spare blocks remaining
You can find these two pieces of information in the disk drive properties, which you can see in
the storage management software by selecting a disk drive on the Physical tab. These are
marked in Figure C-3.
The average erase count is reported as a percentage of the rated lifetime. When the average
erase count reaches 80 percent, an informational event is logged to the Major Event Log
(MEL). At this time, schedule the replacement of the SSD. When the average erase count
reaches 90 percent, a critical event is logged, and a “Needs Attention” condition occurs on the
DS5000. At this time, replace the SSD as soon as possible.
The spare blocks remaining are reported as a percentage of the total blocks. When the spare
blocks remaining falls below 20 percent, an informational event is logged to the MEL. At this
time, schedule the replacement of the SSD. When the spare blocks remaining falls below 10
percent, a critical event is logged, and a “Needs Attention” condition occurs. At this time,
replace the SSD as soon as possible.
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