[tor-relays] 30% drop in exit throughput since Feb 8

[Andy Isaacson]

Noisetor is showing a significant, sustained drop in bandwidth usage
starting approximately February 7-8.  We've checked our setup and logs
and there doesn't appear to be any sign of a causative factor here.

Throughout January and the first week of February we were averaging
400-500 Mbps.  There was a pretty smooth decline down on the 8th,
stabilizing at a "new normal" of 200-300 Mbps which we've maintained
since then.  (All these numbers are based on Munin graphs of eth0
throughput using the if_ plugin.)

I have some hacky Python that summarizes the torstatus.blutmagie.de
data, and it appears that other exits didn't see a similar drop; but our
drop came a few hours to days after torservers added a significant
amount of new bandwidth.  (However, total exit BW reported in torstatus
did not increase much; if anything it seems to have gone down slightly.)
Around the same time, Amunet rose from ~150 Mbps to ~450 Mbps and has
remained in that range since.

Thoughts?

-andy