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Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes" |
Date: |
Tue, 24 Aug 2010 14:35:06 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.11) Gecko/20100720 Fedora/3.0.6-1.fc12 Thunderbird/3.0.6 |
Am 24.08.2010 14:27, schrieb Avi Kivity:
> On 08/24/2010 03:21 PM, Alexander Graf wrote:
>> Avi Kivity wrote:
>>> On 08/24/2010 03:12 PM, Alexander Graf wrote:
>>>>> Well, safety is not boolean. Considering to make it mostly safe instead
>>>>> of completely safe because of the performance doesn't mean that we
>>>>> should make it completely unsafe.
>>>>>
>>>> What is safety then? A vague feeling of "oh today is monday so my data
>>>> is safe, but on tuesday I always lose my image data"? Either we promise
>>>> to keep data safe or we don't. There is no in between.
>>>>
>>> Do you drive a car?
>> Would you buy a car where the breaks are known to not always work? ;)
>
> That's not the case, even with cache=unsafe.
>
>>> Though in general I agree we shouldn't compromise on data integrity.
>> That's my point. Either we go for it or we don't.
>
> I don't know how bad the performance regression is, and how large the
> integrity risk is. I'd default towards preserving integrity, but maybe
> this situation is different.
I have reports of installations taking like 50 min instead of 14 min. My
own qemu-io based test goes up from 1 s to 23 s. And I think the winner
is Michael's image conversion which went up from 30 s to 49 min.
So it's not like we're talking about just some 10 or 20 percent.
Kevin
- [Qemu-devel] [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Kevin Wolf, 2010/08/24
- [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Stefan Hajnoczi, 2010/08/24
- [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Michael Tokarev, 2010/08/24
- [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Kevin Wolf, 2010/08/24
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Alexander Graf, 2010/08/24
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Kevin Wolf, 2010/08/24
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Alexander Graf, 2010/08/24
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Avi Kivity, 2010/08/24
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Alexander Graf, 2010/08/24
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Avi Kivity, 2010/08/24
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes",
Kevin Wolf <=
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Avi Kivity, 2010/08/24
- Re: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Kevin Wolf, 2010/08/24
- [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Stefan Hajnoczi, 2010/08/24
- [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Michael Tokarev, 2010/08/24
[Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Juan Quintela, 2010/08/24
[Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes", Anthony Liguori, 2010/08/24