From: Jamie Lokier <jamie@shareable.org>
To: Chunqiang Tang <ctang@us.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Stefan Hajnoczi <stefanha@gmail.com>,
qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249%
Date: Wed, 19 Jan 2011 00:59:53 +0000 [thread overview]
Message-ID: <20110119005953.GJ30268@shareable.org> (raw)
In-Reply-To: <OFA7461753.169A4475-ON8525781C.006C4C64-8525781C.0070F9C9@us.ibm.com>
Chunqiang Tang wrote:
> Doing both fault injection and verification together introduces some
> subtlety. For example, even under the random failure mode, two disk writes
> triggered by one VM-issued write must either fail together or succeed
> together. Otherwise, the truth image and the test image will diverge and
> verification won't succeed. Currently, qemu-test carefully works with the
> 'sim' driver to guarantee those conditions. Those conditions need be
> retained after code restructure.
If the real backend is a host system file or device, and AIO or
multi-threaded writes are used, you can't depend on two parallel disk
writes (triggered by one VM-issued write) failing together or
succeeding together. All you can do is look at the error code after
each operation completes, and use it to prevent issuing later
operations. You can't stop the other parallel operations that are
already in progress.
Is that an issue in your design assumptions?
Thanks,
-- Jamie
next prev parent reply other threads:[~2011-01-19 1:00 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-04 21:44 [Qemu-devel] [RFC] Propose the Fast Virtual Disk (FVD) image format that outperforms QCOW2 by 249% Chunqiang Tang
2011-01-05 17:29 ` Anthony Liguori
2011-01-14 20:56 ` Chunqiang Tang
2011-01-19 1:12 ` Jamie Lokier
2011-01-19 8:10 ` Stefan Hajnoczi
2011-01-19 15:17 ` Chunqiang Tang
2011-01-19 15:25 ` Christoph Hellwig
2011-01-19 23:56 ` Jamie Lokier
2011-01-19 15:51 ` Christoph Hellwig
2011-01-19 16:21 ` Chunqiang Tang
2011-01-19 16:42 ` Christoph Hellwig
2011-01-19 17:08 ` Chunqiang Tang
2011-01-19 17:25 ` Christoph Hellwig
2011-01-06 9:17 ` Stefan Hajnoczi
2011-01-15 3:28 ` Chunqiang Tang
2011-01-15 17:27 ` Stefan Weil
2011-01-20 2:59 ` Chunqiang Tang
[not found] ` <AANLkTinw2S2dzKoeFK-dBP6b36J+VNLjb3f-vbkKm3Fz@mail.gmail.com>
2011-01-17 10:37 ` Stefan Hajnoczi
2011-01-18 20:35 ` Chunqiang Tang
2011-01-19 0:59 ` Jamie Lokier [this message]
2011-01-19 14:59 ` Chunqiang Tang
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