From: NeilBrown <neilb@suse.de>
To: Martin Wilck <mwilck@arcor.de>
Cc: linux-raid@vger.kernel.org
Subject: Re: ddf: remove failed devices that are no longer in use ?!?
Date: Tue, 30 Jul 2013 11:34:35 +1000 [thread overview]
Message-ID: <20130730113435.3421a111@notabene.brown> (raw)
In-Reply-To: <51F2E4B9.1020505@arcor.de>
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On Fri, 26 Jul 2013 23:06:01 +0200 Martin Wilck <mwilck@arcor.de> wrote:
> Hi Neil,
>
> here is another question. 2 years ago you committed c7079c84 "ddf:
> remove failed devices that are no longer in use", with the reasoning "it
> isn't clear what (a phys disk record for every physically attached
> device) means in the case of soft raid in a general purpose Linux computer".
>
> I am not sure if this was correct. A common use case for DDF is an
> actual BIOS fake RAID, possibly dual-boot with a vendor soft-RAID driver
> under Windows. Such other driver might be highly confused by mdadm
> auto-removing devices. Not even "missing" devices need to be removed
> from the meta data in DDF; they can be simply marked "missing".
>
> May I ask you to reconsider this, and possibly revert c7079c84?
> Martin
You may certainly ask ....
I presumably had a motivation for that change. Unfortunately I didn't record
the motivation, only the excuse.
It probably comes down to a question of when *do* you remove phys disk
records?
I think that if I revert that patch we could get a situation where we keep
adding new phys disk records and fill up some table.
We should probably be recording some sort of WWN or path identifier in the
metadata and then have md check in /dev/disk/by-XXX to decide if the device
has really disappeared or is just failed.
Maybe the 'path' field in phys_disk_entry could/should be used here. However
we the BIOS might interpret that in a specific way that mdadm would need to
agree with....
If we can come up with a reasonably reliable way to remove phys disk records
at an appropriate time, I'm happy to revert this patch. Until then I'm not
sure it is a good idea.....
But I'm open to being convinced.
Thanks,
NeilBrown
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next prev parent reply other threads:[~2013-07-30 1:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-26 21:06 ddf: remove failed devices that are no longer in use ?!? Martin Wilck
2013-07-30 1:34 ` NeilBrown [this message]
2013-07-30 19:24 ` Martin Wilck
2013-07-31 3:25 ` NeilBrown
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