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From: Alberto Garcia <berto@igalia.com>
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Date: Fri, 26 May 2017 15:08:43 +0200
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Subject: Re: [Qemu-devel] [PATCH 0/7] qcow2: Reduce the number of I/O ops
 when doing COW
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To: Anton Nefedov <anton.nefedov@virtuozzo.com>, Kevin Wolf <kwolf@redhat.com>
Cc: Eric Blake <eblake@redhat.com>, qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz <mreitz@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, "Denis V . Lunev" <den@openvz.org>

On Fri 26 May 2017 02:47:55 PM CEST, Anton Nefedov wrote:
> Tried the another machine; about 10% improvement here
  [...]
> [root@localhost ~]# fio --name=randwrite --blocksize=4k
> --filename=/dev/sdb --rw=randwrite --direct=1 --ioengine=libaio
> --size=2g --io_size=32m

In my tests I sometimes detected slight performance decreases in that
HDD scenario but using 'write' instead of 'randwrite' (and --runtime=60
instead of --io_size).

Can you try and see how that works for you?

Berto