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From: Anthony Liguori <anthony@codemonkey.ws>
To: "Daniel P. Berrange" <berrange@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [6388] Stop VM on ENOSPC error.
Date: Wed, 25 Feb 2009 12:31:00 -0600	[thread overview]
Message-ID: <49A58E64.3020303@codemonkey.ws> (raw)
In-Reply-To: <20090225173429.GV24969@redhat.com>

Daniel P. Berrange wrote:
> On Wed, Feb 25, 2009 at 07:04:22PM +0200, Gleb Natapov wrote:
>   
>> Or even to stop. What guest can do with other errors anyway?
>>     
>
> The idea is that if the guest at least sees the I/O error, then it won't
> continue writing as if everything were OK. It may not be able to continue
> normal operation, but it can at least mark the FS read-only and avoid
> ongoing damage.

This simply doesn't happen in practice.  The FS needs to write data to 
the disk in order to remount it read-only.  Once all writes start 
failing, the errors are cascading.

>  So you have a reasonable liklihood of shutting down the
> guest, fixing the ENOSPC problem ont he host, and starting the guests
> again & them recovering their journal.  'ignore' is guarenteed dataloss,
> 'report' gives you a good fighting chance. 'stop'/'enospc' are best, if
> the management app is able to detect that the VM is being paused & thus
> report it to the user
>   
My contention is that a user using a management app is already hosed 
with "report".  To not be fubar, we need async notifications.  If we can 
the default to enospc, I think it makes nothing worse but a good chunk 
of cases a lot better.

Regards,

Anthony Liguori


> Daniel
>   

  reply	other threads:[~2009-02-25 18:31 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-01-21 18:59 [Qemu-devel] [6388] Stop VM on ENOSPC error Anthony Liguori
2009-02-25 16:55 ` Anthony Liguori
2009-02-25 17:04   ` Gleb Natapov
2009-02-25 17:25     ` Avi Kivity
2009-02-25 17:38       ` Jamie Lokier
2009-02-26  9:20         ` Avi Kivity
2009-02-26  9:24           ` Gleb Natapov
2009-02-25 17:34     ` Daniel P. Berrange
2009-02-25 18:31       ` Anthony Liguori [this message]
2009-02-25 18:48         ` Jamie Lokier
2009-02-25 19:29           ` Anthony Liguori
2009-02-25 18:36       ` Jamie Lokier
2009-02-25 17:11   ` Avi Kivity
2009-02-25 18:26     ` Anthony Liguori
2009-02-26  9:17       ` Avi Kivity
2009-02-25 17:20   ` Daniel P. Berrange
2009-02-25 18:08     ` [Qemu-devel] " Jan Kiszka
2009-02-25 18:27     ` [Qemu-devel] " Anthony Liguori
2009-02-25 18:51     ` Jamie Lokier

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