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Comment by spullara | Hacker News Reader

When I put together my home 8-disk server back in 2009 it was pretty clear to me I needed to protect against 2 failures. Even if you just look at the 12 hour recovery times.

How much does this change if you are using modern SSDs?

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I believe that SSDs fail differently, in some respects. If your SSDs "wears out", you may not be able to reprogram it (write to it), but you may still be able to read from it.

Edit: Apparently this is wrong. Read comments below

My experience as we use SSDs for our embedded solutions and sometimes have very frequent writes is that when it goes the whole partition is pretty much hosed. I'm not sure what exactly fails but it seems like the file system index or journal goes and then the whole partition is mostly useless. We use a write filter to avoid writes to OS partition (writes redirect changes to memory) so it is mostly readonly but it still can fail and and when it does the system is unrecoverable. Other partitions may still be seemingly okay but we just replace once a failure is spotted. Disk based drives usually don't fail as catastrophically in my experience but do have more errors.

Having said that we have been using them for past 5 years and only have had a dozen failures in that time over probably 500 deployments. And I think several of those were service replacing because they could not determine a root cause. Fortunately, we don't really have to try to recover anything from the drives but it does cause downtime when they fail.

In your experience, when you had those 12 failures, did drives die suddenly or was it "expectable" because of high usage (high wear)?

what is your gut feeling on failure rate vs standard disks?

I think it probably depends on the quality of the SSD firmware.

unrecoverable? as in, not read-only?

When SSDs fail, they can leave the entire disk unreadable. Spinning disks will usually only corrupt or deny access to a small part. This is very bad if you do not have backups. Beware! http://www.gundersen.net/solid-state-drives-the-best-of-driv...

I had an SSD fail on a mac and the symptoms were that blocks would become intermittently unreadable the longer the drive was running. So when I took it to the genius bar, their tests passed initially. The logs of course showed the read failures, which is what I had to use to convince them the SSD was failing.

Well, in theory it should be true.

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