linux-kernel - Re: [Scst-devel] Fwd: Re: linuxcon 2010...

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Date:	Mon, 23 Aug 2010 14:03:26 -0400
From:	Chetan Loke <chetanloke@...il.com>
To:	Bart Van Assche <bvanassche@....org>
Cc:	landman@...lableinformatics.com,
	James Bottomley <James.Bottomley@...e.de>,
	Vladislav Bolkhovitin <vst@...b.net>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	scst-devel <scst-devel@...ts.sourceforge.net>
Subject: Re: [Scst-devel] Fwd: Re: linuxcon 2010...

I actually received 3+ off-post emails asking whether I was talking
about initiator or target in the 100K IOPS case below and what did I
mean by the ACKs.
I was referring to the 'Initiator' side.
ACKs == When scsi-ML down-calls the LLD via the queue-command, process
the sgl's(if you like) and then trigger the scsi_done up-call path.

Chetan Loke

On Mon, Aug 23, 2010 at 12:07 PM, Chetan Loke <chetanloke@...il.com> wrote:
> On Mon, Aug 23, 2010 at 11:11 AM, Bart Van Assche <bvanassche@....org> wrote:
>
>>
>> There is an important design difference between SCST and LIO: SCST by
>> defaults creates multiple threads to process the I/O operations for a
>> storage target, while LIO only creates a single thread per storage target.
>> This makes SCST perform measurably faster.
>>
>
> Forget that. You could have discussed this if there were code reviews
> or other mainline inclusion emails from James B. From what I have
> heard, the decision was taken around 8-9 months back.
> Would anyone like to either comment/validate/refute this please?  If
> not then I would kindly request these guys to stop taking us for a
> test drive. And also I'm not sure when was the last time James B.
> bench-marked our scsi-stack. Even if I ACK in the xmit-path then I
> can't push more than 100K IOPs. But other folks have re-engineered our
> linux-scsi stack and from what I've heard they can push > 300K+ IOPs.
> So I would just ignore performance discussion because I don't think
> folks have done even simple lame experiments in the last 1 year. Or
> may be I'm completely wrong and so please enlighten me so that I can
> re-run the tests.
>
>
>> Bart.
>>
> Chetan Loke
>
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