[OpenAFS] Re: Maximum disk cache size

Jeffrey Hutzelman jhutz@cmu.edu
Mon, 31 Oct 2005 11:08:57 -0500

On Monday, October 31, 2005 09:18:31 AM -0500 Joe Buehler 
<jbuehler@spirentcom.com> wrote:

> chas williams - CONTRACTOR wrote:
>> there have been some discussions on the openafs-devel list recently about
>> cache tuning.  check the archives.  the 1.4.x branch also has the "new"
>> default cache tuning (auto chunksize selection and different assumption
>> for average file size).
>> if you gave us a little more information some others might be able
>> to make some educated guesses.
> OK, I did some reading and think I understand what is going on.
> There appear to be 3 main parameters:
> - cache size (cacheinfo file)
> - chunk size (afsd argument -chunksize)
> - number of cache files (afsd argument -files)
> Default behavior is for afsd to use a chunk size of 64k and to
> calculate the number of cache files based on the cache size and
> an assumption of average cached file size of about 10k.

That was the default behavior in 1.2.  As Chas pointed out, there have
been several changes to the heuristics since then, largely on the basis
of discussions that occurred on the mailing list.  There are quite a lot
of tuning parameters, but under normal circumstances running 1.4 you
shouldn't need to touch any of them.

-- Jeffrey T. Hutzelman (N3NHS) <jhutz+@cmu.edu>
   Sr. Research Systems Programmer
   School of Computer Science - Research Computing Facility
   Carnegie Mellon University - Pittsburgh, PA