Re: storage over IP (was Re: [PLEASE-TESTME] Zerocopy networking patch,

Re: storage over IP (was Re: [PLEASE-TESTME] Zerocopy networking patch,

[Cacophonix]

I haven't tracked the IP storage group too closely, but was at the San Diego IETF
where there were some interesting debates about this issue. 

There is a write-up at http://ips.pdl.cs.cmu.edu/mail/msg02598.html

Now I'm not sure if I agree with some of the assumptions. And I share your concern 
about using multiple tcp streams.

Thoughts?

cheers,
karthik


--- Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> > <http://www.ietf.org/internet-drafts/draft-ietf-ips-fcovertcpip-01.txt>
> > show that both use TCP/IP.  TCP/IP has variable length headers (or am i on
> > crack?), which totally complicates the receive path.
> 
> TCP has variable length headers. It also prevents you re-ordering commands
> in the stream which would be beneficial. I've not checked if the draft uses
> multiple TCP streams but then you have scaling questions. 
> 
> Alan
> 


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Re: storage over IP (was Re: [PLEASE-TESTME] Zerocopy networking patch,

[Alan Cox]

> fixed length headers).  i've never investigated the actual protocols
> though so maybe the solution used was to just push a lot of the detail
> down into the controllers.

The stuff I have access to (MPT fusion) pushes the FC handling down onto the
board. Basically you talk scsi and IP to it (See drivers/message/fusion in
-ac)

> <http://www.ietf.org/internet-drafts/draft-ietf-ips-fcovertcpip-01.txt>
> show that both use TCP/IP.  TCP/IP has variable length headers (or am i on
> crack?), which totally complicates the receive path.

TCP has variable length headers. It also prevents you re-ordering commands
in the stream which would be beneficial. I've not checked if the draft uses
multiple TCP streams but then you have scaling questions. 

Alan

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