Re: Integration of SCST in the mainstream Linux kernel

[Vladislav Bolkhovitin <vst@vlnb.net>]

FUJITA Tomonori wrote:
> On Wed, 30 Jan 2008 09:38:04 +0100
> "Bart Van Assche" <bart.vanassche@gmail.com> wrote:
> 
> 
>>On Jan 30, 2008 12:32 AM, FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
>>
>>>iSER has parameters to limit the maximum size of RDMA (it needs to
>>>repeat RDMA with a poor configuration)?
>>
>>Please specify which parameters you are referring to. As you know I
> 
> 
> Sorry, I can't say. I don't know much about iSER. But seems that Pete
> and Robin can get the better I/O performance - line speed ratio with
> STGT.
> 
> The version of OpenIB might matters too. For example, Pete said that
> STGT reads loses about 100 MB/s for some transfer sizes for some
> transfer sizes due to the OpenIB version difference or other unclear
> reasons.
> 
> http://article.gmane.org/gmane.linux.iscsi.tgt.devel/135
> 
> It's fair to say that it takes long time and need lots of knowledge to
> get the maximum performance of SAN, I think.
> 
> I think that it would be easier to convince James with the detailed
> analysis (e.g. where does it take so long, like Pete did), not just
> 'dd' performance results.
> 
> Pushing iSCSI target code into mainline failed four times: IET, SCST,
> STGT (doing I/Os in kernel in the past), and PyX's one (*1). iSCSI
> target code is huge. You said SCST comprises 14,000 lines, but it's
> not iSCSI target code. The SCSI engine code comprises 14,000
> lines. You need another 10,000 lines for the iSCSI driver. Note that
> SCST's iSCSI driver provides only basic iSCSI features. PyX's iSCSI
> target code implemenents more iSCSI features (like MC/S, ERL2, etc)
> and comprises about 60,000 lines and it still lacks some features like
> iSER, bidi, etc.
> 
> I think that it's reasonable to say that we need more than 'dd'
> results before pushing about possible more than 60,000 lines to
> mainline.

Tomo, please stop counting in-kernel lines only (see 
http://lkml.org/lkml/2007/4/24/364). The amount of the overall project 
lines for the same feature set is a lot more important.

> (*1) http://linux-iscsi.org/
>