From: Paolo Bonzini <pbonzini@redhat.com>
To: Andrew Martin <amartin@xes-inc.com>,
Stefan Hajnoczi <stefanha@gmail.com>
Cc: qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later
Date: Tue, 26 Aug 2014 09:03:18 +0200 [thread overview]
Message-ID: <53FC3136.50900@redhat.com> (raw)
In-Reply-To: <280510069.69184.1408990389981.JavaMail.zimbra@xes-inc.com>
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
next prev parent reply other threads:[~2014-08-26 7:03 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1009168463.49610.1408133034828.JavaMail.zimbra@xes-inc.com>
2014-08-15 20:18 ` [Qemu-devel] Using cache=writeback safely on qemu 1.4.0 and later Andrew Martin
2014-08-19 14:59 ` Stefan Hajnoczi
2014-08-19 23:20 ` Andrew Martin
2014-08-21 12:59 ` Stefan Hajnoczi
2014-08-25 18:13 ` Andrew Martin
2014-08-26 7:03 ` Paolo Bonzini [this message]
2014-08-27 14:23 ` Andrew Martin
2014-08-27 14:34 ` Paolo Bonzini
2014-08-27 18:46 ` Andrew Martin
2014-08-27 20:47 ` Paolo Bonzini
2014-08-28 10:22 ` Stefan Hajnoczi
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