[bensyverson]

> Data you collected or data you found? Any idea where it was?

I think it was a lengthy blog post citing manufacturer data, found via the FreeNAS forums. The added safety of RAIDZ2 was a good tradeoff. Someone else on this thread reports they lost two SSDs in rapid succession, which I hear happens sometimes with drives from the same batch. In any event, I felt no need to launch an independent investigation of the math and underlying assumptions.

> Zpool status gives you a per-disk error count. I kind of assumed someone doing a resilver would use that command.

Yes, I did indeed use zpool to do the resilver… I don't recall if there were any read errors on other drives at the time of those failures, but probably not, as the scrub probably would have flagged it. They've all been replaced with higher capacity drives, so at the moment I see "No known data errors"

[Dylan16807]

Okay, interesting. Also to be clear I do think Z2 makes sense in a lot of situations, but I suspect that it's not very dependant on drive size like a lot of people think. If I wanted high reliability I'd use Z2 even with small drives.

Also to reply to your other comment: Personally one extra drive is a small price to pay for the peace of mind.

I achieve peace of mind via backups. For each copy, once I get the AFR below 2% I'm not too fussed about pushing it lower.