scp vs ftp performance on SGI IRIX????????

Rick Jones rick.jones2 at
Fri Nov 7 06:33:03 EST 2003

> Could be as simple as the AIX server may be better at number crunching
> and the IRIX box can't encrypt fast enough to keep up with the stream
> of data.

I suspect that the AIX box was network-bound - given there was a factor of 100
difference in the raw network speed available, I suspect there was quite a bit
of idle time on the AIX system transfering with FTP and so plenty of cycles to
be soaked-up by encryption.

The Irix box was likely not network bound - 1GB of data in 28 seconds is ~36
MB/s, which suggests that either the Irix FTP didn't have a large enough TCP
window, or it was already CPU bound on the FTP (since it was not doing GbE
link-rate - and I'm ass-u-me-ing that the files were cached - if not cached,
that could be a disc limit)  I suspect there would have been fewer idle cycles
waiting for the network, so the added overehead of encryption probably broke the
cycle budget and either took the system even more CPU bound, or took it to a
point of being CPU bound.

rick jones
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