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Date: Thu, 15 Sep 2011 21:27:59 +1000
Message-ID: <CAN05THSE6cg6LDr3+Mv8C9XsSzbhNDdjTpeAkvCNjtMshBzGUw@mail.gmail.com>
From: ronnie sahlberg <ronniesahlberg@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] This patch adds a new block driver : iSCSI
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kwolf@redhat.com, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, dlaor@redhat.com, qemu-devel@nongnu.org, fujita.tomonori@lab.ntt.co.jp, Orit Wasserman <owasserm@redhat.com>, hch@lst.de

On Thu, Sep 15, 2011 at 7:11 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
...
> Perhaps Ronnie has rough performance numbers comparing in-kernel iSCSI with
> libiscsi?

I did some tests some time ago just doing things like 'dd if=/dev/sda
of=/dev/null' on the root disk from within a RHEL guest itself
and performace was comparable.
In some tests libiscsi was a few percent faster, in other tests it was
a few percent slower.
But overall, very unscientifically performed test, performance was not
much different.

Now, I am not an expert on tuning cache or tuning the kernel scsi and
iscsi layer, so I would not really want to make too many statements in
the area other than in some tests I performed, performance was good
enough for my use.


I would be very happy if someone competent in tuning
qemu/scsi/open-iscsi (==that means, not me) would do a real
comparasion.


regards
ronnie sahlberg