Am Dienstag, 11. April 2017, 08:52:06 CEST schrieb Tejun Heo: > > Evidently, how often the SSD will lose the race depends on a platform > > and SSD combination, and also on how often the system is powered off. > > A sluggish firmware that takes its time to cut power can save the day... > > > > > > Observing the effects: > > > > An unclean SSD power-off will be signaled by the SSD device through an > > increase on a specific S.M.A.R.T attribute. These SMART attributes can > > be read using the smartmontools package from www.smartmontools.org, > > which should be available in just about every Linux distro. > > > > smartctl -A /dev/sd# > > > > The SMART attribute related to unclean power-off is vendor-specific, so > > one might have to track down the SSD datasheet to know which attribute a > > particular SSD uses. The naming of the attribute also varies. > > > > For a Crucial M500 SSD with up-to-date firmware, this would be attribute > > 174 "Unexpect_Power_Loss_Ct", for example. > > > > 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. > > 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. The write-up by Henrique has been a very informative and interesting read for me. I wondered about the same question tough. I do have a Crucial M500 and I do have an increase of that counter: martin@merkaba:~[…]/Crucial-M500> grep "^174" smartctl-a-201* smartctl-a-2014-03-05.txt:174 Unexpect_Power_Loss_Ct 0x0032 100 100 000 Old_age Always - 1 smartctl-a-2014-10-11-nach-prüfsummenfehlern.txt:174 Unexpect_Power_Loss_Ct 0x0032 100 100 000 Old_age Always - 67 smartctl-a-2015-05-01.txt:174 Unexpect_Power_Loss_Ct 0x0032 100 100 000 Old_age Always - 105 smartctl-a-2016-02-06.txt:174 Unexpect_Power_Loss_Ct 0x0032 100 100 000 Old_age Always - 148 smartctl-a-2016-07-08-unreadable-sector.txt:174 Unexpect_Power_Loss_Ct 0x0032 100 100 000 Old_age Always - 201 smartctl-a-2017-04-11.txt:174 Unexpect_Power_Loss_Ct 0x0032 100 100 000 Old_age Always - 272 I mostly didn´t notice anything, except for one time where I indeed had a BTRFS checksum error, luckily within a BTRFS RAID 1 with an Intel SSD (which also has an attribute for unclean shutdown which raises). I blogged about this in german language quite some time ago: https://blog.teamix.de/2015/01/19/btrfs-raid-1-selbstheilung-in-aktion/ (I think its easy enough to get the point of the blog post even when not understanding german) Result of scrub: scrub started at Thu Oct 9 15:52:00 2014 and finished after 564 seconds total bytes scrubbed: 268.36GiB with 60 errors error details: csum=60 corrected errors: 60, uncorrectable errors: 0, unverified errors: 0 Device errors were on: merkaba:~> btrfs device stats /home [/dev/mapper/msata-home].write_io_errs 0 [/dev/mapper/msata-home].read_io_errs 0 [/dev/mapper/msata-home].flush_io_errs 0 [/dev/mapper/msata-home].corruption_errs 60 [/dev/mapper/msata-home].generation_errs 0 […] (thats the Crucial m500) I didn´t have any explaination of this, but I suspected some unclean shutdown, even tough I remembered no unclean shutdown. I take good care to always has a battery in this ThinkPad T520, due to unclean shutdown issues with Intel SSD 320 (bricked device which reports 8 MiB as capacity, probably fixed by the firmware update I applied back then). The write-up Henrique gave me the idea, that maybe it wasn´t an user triggered unclean shutdown that caused the issue, but an unclean shutdown triggered by the Linux kernel SSD shutdown procedure implementation. Of course, I don´t know whether this is the case and I think there is no way to proof or falsify it years after this happened. I never had this happen again. Thanks, -- Martin
