[stgt] iscsi load generator and benchmark tool

[ronnie sahlberg]

On Fri, Sep 25, 2009 at 9:57 PM, FUJITA Tomonori
<fujita.tomonori at lab.ntt.co.jp> wrote:
> On Fri, 25 Sep 2009 14:39:59 +1000
> ronnie sahlberg <ronniesahlberg at gmail.com> wrote:
>
>> You might find this tool useful.
>> I recently added very simple iscsi support to DBENCH ( http://dbench.samba.org )
>> so that dbench has a minimal iscsi initiator built in.
>>
>> This is sometimes useful since it allows to bypass any iscsi initiator
>> layer, like open-iscsi, on the host and to get full control of exactly
>> what commands will be issued to the target and accurate measures since
>> one can know that the data was served across the network and not from
>> a local cache.
>
> Sounds interesting but you need to put the iscsi initiator feature
> into dbench?
>
> I mean that if dbench issues SCSI commands via sg from a load file,
> can you can achieve similar things?

In theory yes. In practice no.
I could never reach very high workloads using the sg interface but
using the iscsi backend to dbench I could easily generate 100s of
thousands of i/o per second.
I guess the queueing and i/o scheduling of the kernel comes in the way
and interferes.
Using a tiny initiator built into dbench I avoid all interference from
the kernel.
(dbench can also generate I/O directly to a sd device)

>
>
> btw, I got the latest code from the git tree, but seems that there is
> no iscsi support yet.
>


Oh, sorry about that. the webpage had a regression.

The correct git tree is :

 git+ssh://git.samba.org/data/git/sahlberg/dbench.git

Please try this tree.
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