Re: iSCSI: error recovery

[Matt Wakeley <matt_wakeley@agilent.com>]

julian_satran@il.ibm.com wrote:

> Matt,
>
> I think I read your note and I still maintain that the target will fare
> better and the initiator does not have to do anything different.
>
> When failing over the initiator will reissue the command (including all
> scatter gather lists) to the new HBA. It is the target that will send only
> the buffers he has and as long as the initiator is not scoreboarding it
> does not have to do anything different the second time than first.

You are making the *big* assuption that an iSCSI initiator will "confirm" the
receipt of this "numbered" data after the data has been transfered to initiator
host memory.  What if it's buffered on the card somewhere, and the card dies
and the system fails over to a different card?  (or perhaps an I/O subsystem
fails and the system "fails over" to a standby subsystem) How is the initiator
going to be absolutely sure that the "partial" I/O on the first card plus the
"partial" I/O on the second card equal a complete error free I/O?

Is this idea for something that rarely happens really worth the effort?  In the
interests of simplicity, I propose that data not be numbered.


>
>
> It is the target that will benefit and it is the target's decision to
> number or not.
>
> Regards,
> Julo

-Matt