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

Vladislav Bolkhovitin
2008-02-01T12:13:58Z

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