From: Anthony Liguori <anthony@codemonkey.ws>
To: Ryan Harper <ryanh@us.ibm.com>
Cc: Henrik Holst <henrik@witsbits.com>, kvm@vger.kernel.org
Subject: Re: qcow2 slowdown in kvm-78,79
Date: Wed, 19 Nov 2008 12:26:41 -0600 [thread overview]
Message-ID: <49245A61.9050504@codemonkey.ws> (raw)
In-Reply-To: <20081119182317.GA31893@us.ibm.com>
Ryan Harper wrote:
> * Henrik Holst <henrik@witsbits.com> [2008-11-18 08:42]:
>
>> The bundled qemu in kvm-78 and kvm-79 slows down disk i/o with qcow2
>> images by an order of 10. If one got 60MB/s before, one gets around
>> 6MB/s with 78 and 79 (measured with dd)
>>
>
> dd command?
>
> what's your -drive parameters look like, specifically, what if type?
> ide, scsi, virtio?
>
This is probably the change to cache=writethrough. I bet if you set
cache=writeback then you'll see this go away.
qcow needs some love.
Regards,
Anthony Liguori
next prev parent reply other threads:[~2008-11-19 18:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-18 14:39 qcow2 slowdown in kvm-78,79 Henrik Holst
2008-11-19 17:55 ` Thomas Mueller
2008-11-19 18:23 ` Ryan Harper
2008-11-19 18:26 ` Anthony Liguori [this message]
2008-11-19 19:49 ` Thomas Mueller
2008-11-19 22:06 ` Anthony Liguori
2008-11-19 23:47 ` walt
2008-11-20 1:00 ` Anthony Liguori
2008-11-20 7:57 ` Henrik Holst
2008-11-20 8:08 ` Henrik Holst
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