linux-kernel - Re: [Scst-devel] Integration of SCST in the mainstream Linux kernel

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Message-ID: <47A3078C.10704@vlnb.net>
Date:	Fri, 01 Feb 2008 14:50:36 +0300
From:	Vladislav Bolkhovitin <vst@...b.net>
To:	David Dillow <dillowda@...l.gov>
CC:	Bart Van Assche <bart.vanassche@...il.com>,
	landman@...lableinformatics.com,
	James.Bottomley@...senpartnership.com, linux-scsi@...r.kernel.org,
	rdreier@...co.com, linux-kernel@...r.kernel.org,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	fujita.tomonori@....ntt.co.jp, scst-devel@...ts.sourceforge.net,
	akpm@...ux-foundation.org, FUJITA Tomonori <tomof@....org>,
	torvalds@...ux-foundation.org
Subject: Re: [Scst-devel] Integration of SCST in the mainstream Linux kernel

David Dillow wrote:
> On Thu, 2008-01-31 at 18:08 +0100, Bart Van Assche wrote:
> 
>>If anyone has a suggestion for a better test than dd to compare the
>>performance of SCSI storage protocols, please let it know.
> 
> 
> xdd on /dev/sda, sdb, etc. using -dio to do direct IO seems to work
> decently, though it is hard (ie, impossible) to get a repeatable
> sequence of IO when using higher queue depths, as it uses threads to
> generate multiple requests.

This utility seems to be a good one, but it's basically the same as 
disktest, although much more advanced.

> You may also look at sgpdd_survey from Lustre's iokit, but I've not done
> much with that -- it uses the sg devices to send lowlevel SCSI commands.

Yes, it might be worth to try. Since fundamentally it's the same as 
O_DIRECT dd, but with a bit less overhead on the initiator side (hence 
less initiator side latency), most likely it will show ever bigger 
difference, than it is with dd.

> I've been playing around with some benchmark code using libaio, but it's
> not in generally usable shape.
> 
> xdd:
> http://www.ioperformance.com/products.htm
> 
> Lustre IO Kit:
> http://manual.lustre.org/manual/LustreManual16_HTML/DynamicHTML-20-1.html

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