On Sun, 2017-05-07 at 22:40 +0200, Pavel Machek wrote:

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NOTE: unclean SSD power-offs are dangerous and may brick the device in
the worst case, or otherwise harm it (reduce longevity, damage flash
blocks).  It is also not impossible to get data corruption.

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I get that the incrementing counters might not be pretty but I'm a bit
skeptical about this being an actual issue.  Because if that were
true, the device would be bricking itself from any sort of power
losses be that an actual power loss, battery rundown or hard power off
after crash.

And that's exactly what users see. If you do enough power fails on a
SSD, you usually brick it, some die sooner than others. There was some
test results published, some are here
http://lkcl.net/reports/ssd_analysis.html, I believe I seen some
others too.

It is very hard for a NAND to work reliably in face of power
failures. In fact, not even Linux MTD + UBIFS works well in that
regards. See
http://www.linux-mtd.infradead.org/faq/ubi.html. (Unfortunately, its
down now?!). If we can't get it right, do you believe SSD manufactures
do?

[Issue is, if you powerdown during erase, you get "weakly erased"
page, which will contain expected 0xff's, but you'll get bitflips
there quickly. Similar issue exists for writes. It is solveable in
software, just hard and slow... and we don't do it.]

It's not that hard. We certainly do it in JFFS2. I was fairly sure that
it was also part of the design considerations for UBI — it really ought
to be right there too. I'm less sure about UBIFS but I would have
expected it to be OK.

SSDs however are often crap; power fail those at your peril. And of
course there's nothing you can do when they do fail, whereas we accept
patches for things which are implemented in Linux.