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Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later |
Date: |
Tue, 26 Aug 2014 09:03:18 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 |
Il 25/08/2014 20:13, Andrew Martin ha scritto:
> Even if the python daemon or apache2 did not fsync the modified files, isn't
> there some action that the OS takes periodically to flush dirty pages to
> disk?
> This seems to be implied in the SuSE documentation:
> https://www.suse.com/documentation/sles11/book_kvm/data/sect1_1_chapter_book_kvm.html
> "the normal page cache management will handle commitment to the storage
> device."
... using fsync :)
> 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
- [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 <=
- 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, 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