Re: iSCSI: CmdSN and Retry

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

> An extra handshake that requires a small delay should there
> be a non-sequential event would occur orders of magnitude less often than
> similar waits for TCP.  As this must be a rare event, the wait will be
> insignificant.  

Doug,

The non-sequential event may be rare. However, the handshake should occur
on EVERY I/O to safeguard against that rare event. [if 100% ordering is
attempted.]. 

Strict ordering of 2 commands, say,  A followed by B, imply that : 

A target cannot execute B until the initiator acknowledges Status 
PDU for A. (This implies sequential operation on I/Os on the task set
similar to untagged targets, only greater, because this behaviour is per
session and not even per LUN.)

Since iSCSI applies strict ordering to all commands (well, all non-0 CmdSN
commands), the above behaviour will be required on all I/Os within a
session.

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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