SSD Failure modes

So everyone constantly talks about SSD failure modes and how they die suddenly with no warning and blah blah blah (honestly: everything dies, and sometimes the building burns down, so make sure you have off site backups). But here is an interesting failure mode I found this week. I have two older Intel 80GB SSD’s in a RAID 0 configuration I use for scratch space (e.g. unpacking the Linux Kernel and grepping for stuff). But the RAID 0 array was suddenly very very slow. Since I was retiring that machine anyways I had to wipe it, so I popped in the DBAN disk and started wiping all the drives. It said it would take 79 hours, which seemed a bit excessive:

DBAN screen showing two identical SSDs being wiped with very different results.

DBAN screen showing two identical SSDs being wiped with very different results.

That’s right, you may have missed it, I did the first time, there’s no “K” in the speed listing for the first SSD. It’s writing at 559240 BYTES/second, not Kilobytes. The second drive is writing at a reasonable ~56.5 Megabytes/sec but the first one is writing at 0.53 Megabytes/sec, about 100 times slower. This certainly explains why my RAID 0 was behaving so badly. The kicker is there are not write or read errors off of that first drive, it’s just really, really slow. So I guess the lesson to be learned is you should check if your RAID card/software can tell you drive specific statistics or periodically read/write test your SSD’s individually if things start behaving oddly.

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