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Re: [Qemu-block] qemu exit with pending I/O
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-block] qemu exit with pending I/O |
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Date: |
Mon, 27 Apr 2015 15:03:30 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 |
On 27/04/2015 14:23, Peter Lieven wrote:
> Am 27.04.2015 um 14:11 schrieb Paolo Bonzini:
>>
>> On 27/04/2015 13:51, Peter Lieven wrote:
>>>> The reason to do this, is that while I/O is pending you do not know if
>>>> the I/O has been completed or not.
>>> But if I consider a raw image, quitting without a clean shutdown can
>>> also leave an inconsistent state?
>> But you know that all I/O submitted to disk has been handled.
>>
>> The bdrv_drain_all() avoids that some leftover I/O mysteriously pops up
>> while another VM, or another instance of this VM, is using the image.
>> That's much worse.
>
> Can this happen with a raw image used by a single VM?
Yes. Unless the write has been acked or failed explicitly by the
target, you don't know where in the network and storage stack it was lost.
Paolo