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Date: Wed, 09 Jan 2013 11:23:43 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] sheepdog: implement direct write semantics
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To: Kevin Wolf <kwolf@redhat.com>
Cc: Liu Yuan <namei.unix@gmail.com>, qemu-devel@nongnu.org, MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>, Stefan Hajnoczi <stefanha@gmail.com>

Il 08/01/2013 13:12, Kevin Wolf ha scritto:
>> > Okay, I see the code indeed support WCE but it requires Guest kernel to
>> > support it. For the kernel doesn't support it, there is no way to
>> > disable write cache, no?
> With Linux guests, it's possible for SCSI. I'm not sure about
> virtio-blk, but you might be right that you can't manually change it there.

New enough kernels support it.  Also, if you reboot from a system that
supports writeback to one that doesn't (including old-enough Linux), the
new QEMU will be able to use writethrough while running on the older system.

Paolo