From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vladislav Bolkhovitin <vst@vlnb.net>
Subject: Re: Performance of SCST versus STGT
Date: Thu, 24 Jan 2008 22:54:47 +0300
Message-ID: <4798ED07.90000@vlnb.net>
References: <e2e108260801170127w2937b2afg9bef324efa945e43@mail.gmail.com>	 <20080117184052F.fujita.tomonori@lab.ntt.co.jp>	 <478F246C.4040400@vlnb.net>	 <20080117190558K.fujita.tomonori@lab.ntt.co.jp>	 <20080117174542.GC29650@osc.edu>	 <e2e108260801220204k4b914ea1o9b47c0b22c6d098b@mail.gmail.com>	 <4795D4A7.5000105@vlnb.net>	 <e2e108260801220432l353b1d76xd2707b5e6f336aef@mail.gmail.com>	 <20080124070616.GA31633@porcupine.cita.utoronto.ca> <e2e108260801240816n93a234av4368f5e8b3e49bca@mail.gmail.com>
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To: Bart Van Assche <bart.vanassche@gmail.com>
Cc: Robin Humble <robin.humble+stgt@anu.edu.au>, James.Bottomley@hansenpartnership.com, stgt-devel@lists.berlios.de, linux-scsi@vger.kernel.org, FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>, scst-devel@lists.sourceforge.net

Bart Van Assche wrote:
> On Jan 24, 2008 8:06 AM, Robin Humble <robin.humble+stgt@anu.edu.au> wrote:
> 
>>On Tue, Jan 22, 2008 at 01:32:08PM +0100, Bart Van Assche wrote:
>>
>>>.............................................................................................
>>>.                           .   STGT read     SCST read    .    STGT read      SCST read    .
>>>.                           .  performance   performance   .   performance    performance   .
>>>.                           .  (0.5K, MB/s)  (0.5K, MB/s)  .   (1 MB >MB/s)   (1 MB, MB/s)  .
>>>.............................................................................................
>>>. Ethernet (1 Gb/s network) .      77             78       .         77            89       .
>>>. IPoIB    (8 Gb/s network) .     163            185       .        201           239       .
>>>. iSER     (8 Gb/s network) .     250            N/A       .        360           N/A       .
>>>. SRP      (8 Gb/s network) .     N/A            421       .        N/A           683       .
>>>............................................................................................
>>
> 
> Results with /dev/ram0 configured as backing store on the target (buffered I/O):
>                     Read          Write             Read          Write
>                   performance   performance       performance   performance
>                   (0.5K, MB/s)  (0.5K, MB/s)      (1 MB, MB/s)  (1 MB, MB/s)
> STGT + iSER           250          48                 349          781
> SCST + SRP            411          66                 659          746

Ib_rdma_bw now reports 933 MB/s on the same system, correct? Those 
~250MB/s difference is what you will gain with zero-copy IO implemented 
and what STGT with the current architecture has no chance to achieve.

> Results with /dev/ram0 configured as backing store on the target (direct I/O):
>                     Read          Write             Read          Write
>                   performance   performance       performance   performance
>                   (0.5K, MB/s)  (0.5K, MB/s)      (1 MB, MB/s)  (1 MB, MB/s)
> STGT + iSER             7.9         9.8               589          647
> SCST + SRP             12.3         9.7               811          794
> 
> Bart.
>