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

[Vladislav Bolkhovitin <vst@vlnb.net>]

Vladislav Bolkhovitin wrote:
> Bart Van Assche wrote:
> 
>> On Jan 31, 2008 5:25 PM, Joe Landman <landman@scalableinformatics.com> 
>> wrote:
>>
>>> Vladislav Bolkhovitin wrote:
>>>
>>>> Actually, I don't know what kind of conclusions it is possible to make
>>>> from disktest's results (maybe only how throughput gets bigger or 
>>>> slower
>>>> with increasing number of threads?), it's a good stress test tool, but
>>>> not more.
>>>
>>>
>>> Unfortunately, I agree.  Bonnie++, dd tests, and a few others seem to
>>> bear far closer to "real world" tests than disktest and iozone, the
>>> latter of which does more to test the speed of RAM cache and system call
>>> performance than actual IO.
>>
>>
>>
>> I have ran some tests with Bonnie++, but found out that on a fast
>> network like IB the filesystem used for the test has a really big
>> impact on the test results.
>>
>> If anyone has a suggestion for a better test than dd to compare the
>> performance of SCSI storage protocols, please let it know.
> 
> 
> I would suggest you to try something from real life, like:
> 
>  - Copying large file tree over a single or multiple IB links
> 
>  - Measure of some DB engine's TPC
> 
>  - etc.

Forgot to mention. During those tests make sure that imported devices 
from both SCST and STGT report in the kernel log the same write cache 
and FUA capabilities, since they significantly affect initiator's 
behavior. Like:

sd 4:0:0:5: [sdf] Write cache: enabled, read cache: enabled, supports 
DPO and FUA

For SCST the fastest mode is NV_CACHE, refer to its README file for details.

>> Bart Van Assche.
>>
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