From: Mark Trumpold <markt@netqa.com>
To: paolo.bonzini@gmail.com
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] 'qemu-nbd' explicite flush to disk
Date: Mon, 22 Oct 2012 08:10:45 -0700 [thread overview]
Message-ID: <CCAAB005.723A%markt@netqa.com> (raw)
Paolo,
Please recall you had sent me the link below to a kernel patch to allow
'qemu-nbd' to flush to disk. The patch was applied with good success.
However, recent testing indicates that filesystem corruption issue I am
seeing seems to be tied to large (>500mbyte) filesystem writes. I also
observe the kernel 'flush' thread approaching 100% cpu at times, and i/o
wait % as reported by 'top' increasing sharply during the copy/write.
Was wondering if perhaps there are any special kernel config options that
I may be missing for 'nbd', or any other information that might help.
Best regards,
Mark Trumpold
>-----Original Message-----
>From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo
>Bonzini
>Sent: Wednesday, September 12, 2012 11:30 PM
>To: Mark Trumpold
>Cc: qemu-devel@nongnu.org
>Subject: Re: 'qemu-nbd' explicite flush to disk
>Il 12/09/2012 23:28, Mark Trumpold ha scritto:
>> So, I've been experimenting with 'qemu-nbd --cache=writeback ..'
>> This nicely eliminates the 'checkpoint' issue; however, I have as
>> yet been unable to explicitely flush things to disk -- which I would
>>like to
>> do just before a 'nilfs' snapshot.
>The Linux kernel driver for NBD does not support flushes. Patches were
>sent to the maintainer, but he never applied them.
>You can get them at
>http://thread.gmane.org/gmane.linux.drivers.nbd.general/1108 and try
>them.
>> Subsequently I've been trying to call 'bdrv_co_flush(bs)' directly, but
>>I can't
>figure out how to dereference 'bs' for the call.
>>
>> I'm probably out in the weeds on this one.
>> Any guidance would be greatly appreciated.
>>
>> I am running:
>> qemu-1.2.0
>> linux kernel 3.3.1
>>
>> Thank you,
>> Mark Trumpold
next reply other threads:[~2012-10-22 15:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-22 15:10 Mark Trumpold [this message]
2012-10-23 2:50 ` [Qemu-devel] FW: 'qemu-nbd' explicite flush to disk Mark Trumpold
2012-10-24 15:46 ` Paolo Bonzini
-- strict thread matches above, loose matches on Subject: below --
2012-09-12 21:28 [Qemu-devel] " Mark Trumpold
2012-09-13 6:30 ` Paolo Bonzini
2012-09-13 22:01 ` Mark Trumpold
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