Re: [storm] iSER update request from Alex Nezhinsky on WSTAG

[<[e-mail]>]

WG chair hat off:
 
I think I understand what IB is doing, but what's the iWARP behavior?
 
I'm concerned that introduction of a new key that has to be negotiated
may break all the implementations that don't understand the new key.

Thanks,
--David


 


________________________________

	From: [e-mail] [mailto:[e-mail]] On
Behalf Of Mike Ko
	Sent: Friday, August 21, 2009 12:43 AM
	To: STORM
	Subject: [storm] iSER update request from Alex Nezhinsky on
WSTAG
	
	
	Alex sent me the following iSER update request:
	 
	> WSTAG (RKEY+VA for IB) sent by the initiator with a WRITE SCSI
	> command de facto accounts for the offset, associated with the
	> solicited data, and does not reference the entire data. This
happened
	> for historical reasons, but the actual "intuitive" rationale
for that
	> is the fact that the initiator sometimes treats the memory
regions
	> intended for unsolicited and solicited data transfers
differently, as
	> they are carried out using different Infiniband mechanisms
(Send from
	> the initiator, RDMA from the target) that imply different
registration
	> modes. In contrast, the model implied by the iSER spec
creators was
	> that the memory occupied by data is treated as contiguous (or
	> virtually contiguous, by means of scatter-gather mechanisms)
and
	> homogenous region.
	>
	> Suggested solution; either change the spec to align it with
the
	> de-facto implementations, or to add a flag to iSER-Hello
message in
	> order to allow coping with the legacy implementations.
Ironically,
	> iSER-Hello message currently is not implemented either, but we
have to
	> assume that at some point in the future it will be universally
	> available.
	 
	It seems to me there is also a third option other than the two
outlined above.  That is, 
	create a new operational key that conveys how the memory region
will be used.  This avoids having to require the use of iSER Hello
messages if indeed that is not implemented in practise.
	 
	Mike