Re: Race to power off harming SATA SSDs

Martin Steigerwald
2017-04-12T07:47:19Z

Am Dienstag, 11. April 2017, 11:31:29 CEST schrieb Henrique de Moraes
Holschuh:
> On Tue, 11 Apr 2017, Martin Steigerwald wrote:
> > 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).
>
> The Crucial M500 has something called "RAIN" which it got unmodified
> from its Micron datacenter siblings of the time, along with a large
> amount of flash overprovisioning. Too bad it lost the overprovisioned
> supercapacitor bank present on the Microns.

I think I read about this some time ago. I decided for a Crucial M500 cause in
tests it wasn´t the fastest, but there were hints that it may be one of the
most reliable mSATA SSDs of that time.

[… RAIN explaination …]

> > 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.
>
> Maybe. But that corruption could easily having been caused by something
> else. There is no shortage of possible culprits.

Yes.

> I expect most damage caused by unclean SSD power-offs to be hidden from
> the user/operating system/filesystem by the extensive recovery
> facilities present on most SSDs.
>
> Note that the fact that data was transparently (and sucessfully)
> recovered doesn't mean damage did not happen, or that the unit was not
> harmed by it: it likely got some extra flash wear at the very least.

Okay, I understand.

Well my guess back then, I didn´t fully elaborate on it in the initial mail,
but did so in the blog post, was exactly that I didn´t see any capacitor on
the mSATA SSD board. But I know the Intel SSD 320 has capacitors. So I
thought, okay, maybe there really has been a sudden powerloss due to me trying
to exchange battery during suspend to RAM / standby, without me remembering
this event. And I thought, okay, without capacitor the SSD then didn´t get a
chance to write some of the data. But again this also is just a guess.

I can provide to you smart data files in case you want to have a look at them.

> BTW, for the record, Windows 7 also appears to have had (and maybe still
> have) this issue as far as I can tell. Almost every user report of
> excessive unclean power off alerts (and also of SSD bricking) to be
> found on SSD vendor forums come from Windows users.

Interesting.

Thanks,
--
Martin