From: NeilBrown <neilb@suse.de>
To: "." <desire@gmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: software raid and ERC
Date: Wed, 18 Apr 2012 13:52:10 +1000 [thread overview]
Message-ID: <20120418135210.24ff8db5@notabene.brown> (raw)
In-Reply-To: <CAAevFRRh2YiQOe1cbEFc+wY8UnBCEMAvrLdBsQLzfWt-6URpXA@mail.gmail.com>
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On Wed, 18 Apr 2012 11:12:57 +0800 "." <desire@gmail.com> wrote:
> Apart from the behaviour of the SCSI layer, does the linux software
> raid layer have any concept of timeouts that would cause a drive to be
> kicked when performing a deep recovery cycle? A storagereview forum
> thread [3] claims that the linux software raid layer does not have a
> concept of timeouts and does not care about ERC. In a web article [4]
> the major NAS manufacturers that use software raid seem to agree with
> this stance.
Linux software RAID does not have a concept of timeouts.
>
> On the other hand, how I interpret a previous post from Stefan [5] is
> that the linux raid layer does have its own timeout mechanism that
> will kick a non-responding drive.
That aspect of that post is inaccurate.
>
> > Without ERC-timeout, the drive tries to correct the error on
> > its own (not reacting on any requests), mdraid assumes an error after a
> > while and tries to rewrite the "missing" sector (assembled from the
> > other disks). But the drive will still not react to the write request
> > as it is still doing its internal recovery procedure. Now mdraid
> > assumes the disk to be bad and kicks it.
>
> Since I can't read code, I'm hoping that this list where software raid
> development takes place would be able to clear up whether
>
> a. Do delays caused by deep recovery cycles actually have any direct
> impact on the linux software raid layer, or does it simply issue a
> command to the underlying storage/scsi subsystem and block until there
> is a response?
md/raid in linux simply issues a command and waits for it to complete, either
with success or failure.
NeilBrown
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prev parent reply other threads:[~2012-04-18 3:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAAevFRRuGc6x4hJax-kM8ncW9=873aRnjN-WWkoheYD7r6jimA@mail.gmail.com>
2012-04-17 14:05 ` software raid and ERC .
2012-04-17 17:47 ` Emmanuel Noobadmin
2012-04-18 2:08 ` Phil Turmel
2012-04-18 3:12 ` .
2012-04-18 3:52 ` NeilBrown [this message]
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