Re: libata / scsi separation

Grant Grundler
2008-12-10T17:21:52Z

On Wed, Dec 10, 2008 at 7:24 AM, Matthew Wilcox <matthew@wil.cx> wrote:
...
> This would work, but (ignoring the political / standardisation efforts
> required to make this happen), this is just a cop-out. When networking
> people were first faced with gigabit, they tried the same thing (oooh,
> 9000 byte packets, oooh, TCP Offload, etc), all in the name of passing
> larger amounts of data to the card in a single transaction so they
> didn't have to fix their per-transaction overheads.

Willy,
I agree with your points except for one: TCP Offload.

James Bottomley gets credit for publicly observing that storage
protocols have been offloaded for ages. I once worked on a SCSI
controller that interrupted on every phase change (early 90's). Next
generation of SCSI controllers had offload. Same thing occured
to FC in the late 90s and legacy PATA is being replaced with
equivalent SATA offload engines more recently. Enough examples.

> Users weren't interested. They wanted to keep sending 1500 byte packets
> (because most equipment couldn't handle jumbo frames) and they wanted
> netfilter and SACK and all the other goodies that the Linux networking
> stack offered and the card's TCP stack didn't.
>
> We should stop denying that users actually want to do 4k IOs and just
> get on with fixing the storage stack to cope with lots of them.

+1

thanks,
grant