Re: iSCSI: CmdSN and Retry

[Santosh Rao <santoshr@cup.hp.com>]

> Unless the transport maintains order, there will be a requirement to wait
> for each command to complete to assure the sequence.  

Doug, 

The majority of SCSI stacks today DO function as stated above.
The layer above ULP enforces the ordering and awaits completion of 1 I/O
prior to posting the subsequent I/O , PROVIDED those 2 I/Os required
ordering to be maintained.

> This makes 
> compliance to SCSI impossible and not a means of improving the pipe-line.  
Are you saying that the majority of stacks today are not 
SCSI compliant (?)

YP raises a valid concern in that if strict ordering is expected from the
transport, it should be capable of providing this 100 %. (98% strict
ordering is'nt good enough.). To attempt to provide 100% guarantee of
strict ordering is going to prevent concurrent I/O processing at the
target at a session level (NOT even a LUN level, which is the granularity
where one would expect ordering, if at all !).

Regards,
Santosh



-- 
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Santosh Rao
Software Design Engineer,
HP, Cupertino.
email : santoshr@cup.hp.com
Phone : 408-447-3751
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