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Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later
From: |
Andrew Martin |
Subject: |
Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later |
Date: |
Wed, 27 Aug 2014 09:23:45 -0500 (CDT) |
----- Original Message -----
> From: "Paolo Bonzini" <address@hidden>
> To: "Andrew Martin" <address@hidden>, "Stefan Hajnoczi" <address@hidden>
> Cc: "qemu-devel" <address@hidden>
> Sent: Tuesday, August 26, 2014 2:03:18 AM
> Subject: Re: Using cache=writeback safely on qemu 1.4.0 and later
>
> > In the case of the files uploaded by apache2, they were added to the server
> > days
> > before the power outage, so it seems like there would have been ample time
> > for
> > those changes to have been flushed.
>
> Remember that cache=writeback has a huge cache, whose size is several
> gigabytes.
>
> At some point there was a QEMU bug that caused the guest not to do
> fsyncs. It was fixed by commit ef5bc96268.
Paolo,
Thanks for the info about this bug - I am using QEMU 1.4.0 (released on
02/15/13)
and ef5bc96268 was added on 09/20/13, so the bug had not been fixed in the
version
of QEMU I am using. I have had trouble reproducing it on-demand - was there
specific
behavior you used to reproduce it, or just the lack of fsyncs or fdatasyncs when
stracing the QEMU process when using cache=writeback?
Thanks,
Andrew
- [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Andrew Martin, 2014/08/15
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Stefan Hajnoczi, 2014/08/19
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Andrew Martin, 2014/08/19
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Stefan Hajnoczi, 2014/08/21
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Andrew Martin, 2014/08/25
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Paolo Bonzini, 2014/08/26
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later,
Andrew Martin <=
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Paolo Bonzini, 2014/08/27
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Andrew Martin, 2014/08/27
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Paolo Bonzini, 2014/08/27
- Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later, Stefan Hajnoczi, 2014/08/28