[Beowulf] High Performance SSH/SCP
hahn at mcmaster.ca
Thu Feb 14 14:07:36 EST 2008
> Hopefully the PSC folks (or other parties) can convince the OpenSSH
> maintainers to allow some options (dynamic buffers, disabled encryption
> of the non-handshake payload, etc.) that result in higher-bandwidth
the switch-to-none feature is a good one. I'm a bit skeptical about
the buffering changes, since you can accomplish the same thing with
sysctls. (has anyone ever experienced a real case where too-large
sysctl net memory settings caused problems? obviously, attempting
to do long-fat-pipe transfers to a heavily used web server might
be a problem, since the latter wants tight controls on sock mem use.)
the really cool thing would be if you could associate a default
setting for socket buffers with a _route_. heck, a round-port combo.
it seems crazy for apps to be messing with these issues.
> ps - For ssh transfers over long distances (high-bandwith and high
> latency) one can break the data up into pieces and run multiple
> ssh transfers in parallel. Transmitting terabyte data sets from
> the West Coast to the East Coast over Abilene I've seen >10X
> speedups (that is, >10X the overall throughput) when running
> 15--20 simultaneous ssh sessions.
this implies inappropriate buffer size settings, no? what's the bw*delay
product for that path?
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