[stgt] [PATCH] sg-based backing store

[ronnie sahlberg]

On Fri, Oct 17, 2008 at 1:49 AM, Richard Sharpe
<realrichardsharpe at gmail.com> wrote:
> On Thu, Oct 16, 2008 at 1:53 AM, ronnie sahlberg
> <ronniesahlberg at gmail.com> wrote:
>> OFF TOPIC :
>>
>> On Wed, Oct 8, 2008 at 5:14 PM, FUJITA Tomonori
>> <fujita.tomonori at lab.ntt.co.jp> wrote:
>>>
>>> My point is that the performance of read-world workload benchmark like
>>> dbench are relevant for the users than the performances of sequential
>>> accesses.
>>
>>
>> Funny you should mention DBENCH ( http://dbench.samba.org ).
>> I recently added a NFS backend so that dbench can generate raw NFS
>> traffic using "nfs-style" loadfiles. With the ability to take a NFS
>> network trace and convert into one such loadfile automatically.
>>
>> I also recently added a SCSI backend to dbench (though it only handles
>> READ10 and TESTUNITREADY commands so far) with the intent of being
>> able to trace from a kernel the set of all SCSI operations perfromed
>> durign some operation and then use "dbench -B scsi" to replay the
>> exact same set of commands.
>> My vision is that this could then be used to compare different devices
>> how they operate on specific kinds of workloads.
>> Maybe one "loadfile" that records and replays all SCSI i/o that goes
>> to a device while one is recompiling a kernel,    while operating on a
>> very large picture in GIMP, reading a very large document into
>> openoffice, etc etc.
>
> Hmmm, it struck me recently that one could write a simple filter SCSI
> LLD that interposes itself between a real LLD and the SCSI ML and
> captures all CDBs and some of the data on the way through and makes it
> available for a capture program in the same way as the packet capture
> stuff works.
>
> In some ways, this would be more convenient than using iSCSI ...

That would be incredibly useful.
The best would probably be to build this support into libpcap, like
how capturing a USB bus works.
With a new DLT value for pcap for storing raw scsi frames and
pseudoframes we would have a
fileformat defined already and would very easily have instant support
in many applications that already operate on sequences of frames.


ronnie sahlberg
--
To unsubscribe from this list: send the line "unsubscribe stgt" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html