[HCoop-Discuss] local advocacy

[David Crawshaw]

Adam Megacz <megacz at hcoop.net>:
>  Are you still using BigPond?  Pings from mire to them are only 250ms,
>  which must make SSH really annoying, but isn't "high latency" from
>  AFS's perspective (indeed, back in the 80's when AFS was developed
>  that was probably considered a "normal" ping time).
>
>  If you are experiencing packet loss, that may affect AFS more severely
>  than TCP-based protocols.  But you should switch providers if you're
>  getting packet loss on a regular basis -- that is not normal.

No serious packet loss here. And while your theory about 250ms not
being slow for AFS is a good one, evidence seems to suggest that Rx
has trouble adapting to the link. Testing different file sizes:

  75KB: scp is 4.7 times faster
 161KB: scp is 2.5 times faster
1000KB: scp is 1.6 times faster

(This is with scp establishing a new connection each time, which has
some significant overhead, so the small file results are if anything,
understated.)

Now it might not be latency, it might be some crazy burst-iness of the
link, or this might just be noise because I didn't run the tests
enough times, but something seems amiss.

Anyway, I don't have the time to dedicate to an analysis right now.

d.


$ time cp hcoop-a4-draft.pdf /afs/hcoop.net/user/c/cr/crawshaw/public_html/

real	0m41.258s
user	0m0.001s
sys	0m0.011s

$ time scp hcoop-a4-draft.pdf mire:public_html
hcoop-a4-draft.pdf                            100%  161KB  32.2KB/s   00:05

real	0m16.104s
user	0m0.074s
sys	0m0.040s

$ time cp smile-lecture1.pdf /afs/hcoop.net/user/c/cr/crawshaw/

real	3m59.237s
user	0m0.001s
sys	0m0.009s

$ time scp smile-lecture1.pdf mire:~
smile-lecture1.pdf                            100% 1000KB   8.1KB/s   02:03

real	2m29.108s
user	0m0.121s
sys	0m0.068s

time cp rx-spec.pdf /afs/hcoop.net/user/c/cr/crawshaw/
cp: /afs/hcoop.net/user/c/cr/crawshaw/rx-spec.pdf: Operation timed out

real	0m57.294s
user	0m0.001s
sys	0m0.003s

$ time scp rx-spec.pdf mire:~
rx-spec.pdf                                   100%   75KB  75.0KB/s   00:01

real	0m12.135s
user	0m0.069s
sys	0m0.039s