[OpenAFS] Performance issue with "many" volumes in a single /vicep?

Derrick Brashear shadow@gmail.com
Wed, 17 Mar 2010 19:41:59 -0400

On Wed, Mar 17, 2010 at 12:50 PM, Steve Simmons <scs@umich.edu> wrote:
> We've been seeing issues for a while that seem to relate to the number of=
 volumes in a single vice partition. The numbers and data are inexact becau=
se there are so many damned possible parameters that affect performance, bu=
t it appears that somewhere between 10,000 and 14,000 volumes performance f=
alls off significantly. That 40% difference in volume count results in 2x t=
o 3x falloffs for performance in issues that affect the /vicep as a whole -=
 backupsys, nightly dumps, vos listvol, etc.
> My initial inclination is to say it's a linux issue with directory search=
es, but before pursuing this much further I'd be interested in hearing from=
 anyone who's running 14,000 or move volumes in a single vicep. No, I'm not=
 counting .backup volumes in there, so 14,000 volumes means 28,000 entries =
in the directory.

Another possibility: there's a hash table which is taking the bulk of
that that you then search linearly.