Re: iSCSI ERT: data SACK/replay buffer/"semi-transport"

[Pierre Labat <pierre_labat@hp.com>]

julian_satran@il.ibm.com wrote:

> SNACK is here for two reasons - Status retry (which is cheap) and Data
> retry as a side benefit.
> CRC errors are not that rare (although we don't have real data the
> simulation with file systems seem to indicate that numbers could be as high
> a 0.0002%).

Julo,

Could you explain how you get this number.
Does it come from
                     J. Stone et. al "Performance of Checksums and CRC's over
Real Data"
                      IEEE/ACM Transactions on Networking, Vol. 6, No. 5,
October 1998

http://dev.acm.org/pubs/articles/journals/ton/1998-6-5/p529-stone/p529-stone.pdf

???
I don't see how you got this number.
What i saw was:
                    Less than 1 escape in 10e17 segments when taking into
                    account the link layer AAL5 CRC. (see page 540 left column
on top).

Regards,

Pierre

> A restart of link - is expensive (slow start) and even if they
> are far lower for many applications a slow start is a painfull event.
>
> Removing them from the spec is not a path we should take lightly.
>
> Julo