der Mouse <mouse@Rodents.Montreal.QC.CA> writes:
> However-- just how much _does_ all that extra overhead reduce
> throughput?  My seat-of-the-pants guess is that it's less than ten
> percent, down in the range where if that little extra bit of
> performance matters to you, you're probably dedicated enough that you
> don't mind having to seek out the right options to get the best
> performance (like using UDP instead of TCP).

It has been a while since I've benchmarked this stuff, but my
recollection is that 10% is about right for full-duplex ethernet.
Classic (half-duplex, CSMA/CD) ethernet with most NICs it is more like
20% due to the ethernet capture effect delaying the ACKs--NFS/UDP gets
up to 90% of wire, TCP maxes out around 70% due to ethernet capture.

> And TCP will certainly help over even slightly lossy networks, for all
> the reasons already mentioned.

Yep--NFSv3 with 32k r/wsize over UDP is a *very* sensitive detector of
network problems, miniscule packet drop rates will make it completely
unusable.
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