Re: Race to power off harming SATA SSDs

From	Ricard Wanderlof <ricard.wanderlof@axis.com>
Newsgroups	linux.kernel
Subject	Re: Race to power off harming SATA SSDs
Date	2017-05-08 11:10 +0200
Message-ID	<tEMQ1-1VT-11@gated-at.bofh.it> (permalink)
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On Mon, 8 May 2017, David Woodhouse wrote:

> > On Mon, 8 May 2017, David Woodhouse wrote:
> > > Our empirical testing trumps your "can never happen" theory :)
> >
> > I'm sure it does. But what is the explanation then? Has anyone analyzed 
> > what is going on using an oscilloscope to verify relationship between 
> > erase command and supply voltage drop?
> 
> Not that I'm aware of. Once we have reached the "it does happen and we
> have to cope" there was not a lot of point in working out *why* it
> happened.
> 
> In fact, the only examples I *personally* remember were on NOR flash,
> which takes longer to erase. So it's vaguely possible that it doesn't
> happen on NAND. But really, it's not something we should be depending
> on and the software mechanisms have to remain in place.

My point is really that say that the problem is in fact not that the erase 
is cut short due to the power fail, but that the software issues a second 
command before the first erase command has completed, for instance, or 
some other situation. Then we'd have a concrete situation which we can 
resolve (i.e., fix the bug), rather than assuming that it's the hardware's 
fault and implement various software workarounds.

On the other hand, making the software resilient to erase problems 
essentially makes the system more robust in any case, so it's not a bad 
thing of course.

It's just that I've seen this "we're software guys, and it must be the 
hardware's fault" (and vice versa) enough times to cause a small warning 
bell to off here.

/Ricard
-- 
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30

Thread

Re: Race to power off harming SATA SSDs Pavel Machek <pavel@ucw.cz> - 2017-05-08 00:00 +0200
  Re: Race to power off harming SATA SSDs David Woodhouse <dwmw2@infradead.org> - 2017-05-08 09:30 +0200
    Re: Race to power off harming SATA SSDs Ricard Wanderlof <ricard.wanderlof@axis.com> - 2017-05-08 09:40 +0200
      Re: Race to power off harming SATA SSDs David Woodhouse <dwmw2@infradead.org> - 2017-05-08 10:20 +0200
        Re: Race to power off harming SATA SSDs Ricard Wanderlof <ricard.wanderlof@axis.com> - 2017-05-08 10:40 +0200
          Re: Race to power off harming SATA SSDs David Woodhouse <dwmw2@infradead.org> - 2017-05-08 11:00 +0200
            Re: Race to power off harming SATA SSDs Ricard Wanderlof <ricard.wanderlof@axis.com> - 2017-05-08 11:10 +0200
              Re: Race to power off harming SATA SSDs Hans de Goede <hdegoede@redhat.com> - 2017-05-08 11:10 +0200
                Re: Race to power off harming SATA SSDs David Woodhouse <dwmw2@infradead.org> - 2017-05-08 12:20 +0200
                Re: Race to power off harming SATA SSDs Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-05-08 14:00 +0200
                Re: Race to power off harming SATA SSDs David Woodhouse <dwmw2@infradead.org> - 2017-05-08 17:50 +0200
                Re: Race to power off harming SATA SSDs Pavel Machek <pavel@ucw.cz> - 2017-05-08 23:40 +0200
                Re: Race to power off harming SATA SSDs Pavel Machek <pavel@ucw.cz> - 2017-05-08 18:50 +0200
                Re: Race to power off harming SATA SSDs Tejun Heo <tj@kernel.org> - 2017-05-08 19:50 +0200
                Re: Race to power off harming SATA SSDs Pavel Machek <pavel@ucw.cz> - 2017-05-08 21:00 +0200
                Re: Race to power off harming SATA SSDs Tejun Heo <tj@kernel.org> - 2017-05-08 21:10 +0200
                RE: Race to power off harming SATA SSDs Atlant Schmidt <aschmidt@dekaresearch.com> - 2017-05-08 20:50 +0200
              Re: Race to power off harming SATA SSDs David Woodhouse <dwmw2@infradead.org> - 2017-05-08 12:20 +0200
    Re: Race to power off harming SATA SSDs Pavel Machek <pavel@ucw.cz> - 2017-05-08 11:30 +0200
      Re: Race to power off harming SATA SSDs David Woodhouse <dwmw2@infradead.org> - 2017-05-08 11:40 +0200
        Re: Race to power off harming SATA SSDs Pavel Machek <pavel@ucw.cz> - 2017-05-08 13:00 +0200
          Re: Race to power off harming SATA SSDs Richard Weinberger <richard.weinberger@gmail.com> - 2017-05-08 13:10 +0200
            Re: Race to power off harming SATA SSDs Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-05-08 14:00 +0200
            Re: Race to power off harming SATA SSDs Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-05-08 14:00 +0200
              Re: Race to power off harming SATA SSDs Richard Weinberger <richard@nod.at> - 2017-05-08 14:20 +0200
          Re: Race to power off harming SATA SSDs David Woodhouse <dwmw2@infradead.org> - 2017-05-08 13:20 +0200
            Re: Race to power off harming SATA SSDs Pavel Machek <pavel@ucw.cz> - 2017-05-08 14:40 +0200
      Re: Race to power off harming SATA SSDs Richard Weinberger <richard.weinberger@gmail.com> - 2017-05-08 12:00 +0200

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