From: NeilBrown <neilb@suse.de>
To: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Dan Williams <dan.j.williams@intel.com>,
linux-raid <linux-raid@vger.kernel.org>
Subject: Re: write-refresh md array (feature request)
Date: Thu, 12 Sep 2013 09:05:48 +1000 [thread overview]
Message-ID: <20130912090548.5613ab26@notabene.brown> (raw)
In-Reply-To: <20130911123222.GA1736@khazad-dum.debian.net>
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On Wed, 11 Sep 2013 09:32:23 -0300 Henrique de Moraes Holschuh
<hmh@hmh.eng.br> wrote:
> On Tue, 10 Sep 2013, Dan Williams wrote:
> > On Tue, Sep 10, 2013 at 11:19 AM, Henrique de Moraes Holschuh
> > <hmh@hmh.eng.br> wrote:
> > > (please CC me on replies).
> > > I've been in several situations where it would have been helpful to be able
> > > to refresh weak sectors by rewriting the whole md raid component device,
> > > without the need to increase array failure risk through a fail+remove+add
> > > cycle for the component device.
> > >
> > > How difficult would it be to implement a "refresh" as a Linux md driver
> > > sync_action, pigging back on "check" ?
> > >
> > > Are there any drawbacks to write-refreshing component devices?
> > >
> >
> > Why is "check" insufficient? If it trips over any bad sectors it will
> > re-write them.
>
> The idea is to rewrite the sector _before_ it goes bad.
>
> Consumer SATA HDDs nowadays not only apparently fail to properly remap
> sectors because they don't track anymore that some sectors in that subtrack
> were reported uncorrect a number of times (and thus are "weak"). They also
> appear to not write-refresh sectors that required ECC correction, except
> maybe during an offline SMART test routine.
>
My view on this is that it has nothing to do with RAID. If it is valuable to
"write-refresh" a device in a RAID array, then it would equally make sense to
write-refresh a device that wasn't in a RAID array.
So any solution to this should try to address the whole problem.
NeilBrown
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next prev parent reply other threads:[~2013-09-11 23:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-10 18:19 write-refresh md array (feature request) Henrique de Moraes Holschuh
2013-09-11 1:25 ` Dan Williams
2013-09-11 12:32 ` Henrique de Moraes Holschuh
2013-09-11 23:05 ` NeilBrown [this message]
2013-09-11 6:41 ` CoolCold
[not found] ` <CAGqmV7ph6JF1cVQwBt-FrzToThMC+gbfPMj3V5EFqbtoOFuFHQ@mail.gmail.com>
2013-09-11 12:37 ` Henrique de Moraes Holschuh
2013-09-11 20:00 ` Dan Williams
2013-09-11 20:15 ` Henrique de Moraes Holschuh
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