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Date: Wed, 1 Apr 2009 22:14:24 +0200
Message-ID: <e2e108260904011314h1e0cf5c5wcdf210eee24d40d8@mail.gmail.com>
Subject: Re: ISCSI-SCST performance (with also IET and STGT data)
From: Bart Van Assche <bart.vanassche@gmail.com>
To: Vladislav Bolkhovitin <vst@vlnb.net>
Cc: scst-devel <scst-devel@lists.sourceforge.net>, linux-scsi@vger.kernel.org,
       linux-kernel@vger.kernel.org, iscsitarget-devel@lists.sourceforge.net,
       stgt@vger.kernel.org
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On Mon, Mar 30, 2009 at 7:33 PM, Vladislav Bolkhovitin <vst@vlnb.net> wrote:
==================================================================
>
> I. SEQUENTIAL ACCESS OVER SINGLE LINE
>
> 1. # dd if=/dev/sdX of=/dev/null bs=512K count=2000
>
> ? ? ? ? ? ? ? ? ? ? ? ?ISCSI-SCST ? ? ?IET ? ? ? ? ? ? STGT
> NULLIO: ? ? ? ? ? ? ? ? 106 ? ? ? ? ? ? 105 ? ? ? ? ? ? 103
> FILEIO/CFQ: ? ? ? ? ? ? 82 ? ? ? ? ? ? ?57 ? ? ? ? ? ? ?55
> FILEIO/deadline ? ? ? ? 69 ? ? ? ? ? ? ?69 ? ? ? ? ? ? ?67
> BLOCKIO/CFQ ? ? ? ? ? ? 81 ? ? ? ? ? ? ?28 ? ? ? ? ? ? ?-
> BLOCKIO/deadline ? ? ? ?80 ? ? ? ? ? ? ?66 ? ? ? ? ? ? ?-

I have repeated some of these performance tests for iSCSI over IPoIB
(two DDR PCIe 1.0 ConnectX HCA's connected back to back). The results
for the buffered I/O test with a block size of 512K (initiator)
against a file of 1GB residing on a tmpfs filesystem on the target are
as follows:

write-test: iSCSI-SCST 243 MB/s; IET 192 MB/s.
read-test: iSCSI-SCST 291 MB/s; IET 223 MB/s.

And for a block size of 4 KB:

write-test: iSCSI-SCST 43 MB/s; IET 42 MB/s.
read-test: iSCSI-SCST 288 MB/s; IET 221 MB/s.

Or: depending on the test scenario, SCST transfers data between 2% and
30% faster via the iSCSI protocol over this network.

Something that is not relevant for this comparison, but interesting to
know: with the SRP implementation in SCST the maximal read throughput
is 1290 MB/s on the same setup.

Bart.
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