[OpenAFS] Caveats of having AFS cache on a shared ext3 partition in Linux?

Simon Wilkinson sxw@inf.ed.ac.uk
Sat, 30 Jan 2010 01:11:48 +0000

There are a number of issues that you will encounter.

Firstly, as you note, there is a danger of the root disk filling. The =
reserved percentage won't help with this - a user process could fill 95% =
of the disk, and the remaining 5% still not be large enough for the AFS =
cache. Sadly, the Unix cache manager is not particularly robust when it =
is unable to write to its cache - the machine will likely panic if this =

Secondly, there are almost certainly going to be performance issues in =
sharing the cache with other data. ext3 is not particularly performant =
compared to ext2, and sharing the ext3 journal between your cache =
filesystem and the rest of the system won't aid in this. The fact that =
we goofed the setting of the "don't update the access time" flag on =
cache accesses won't aid you either.

That said, I know of lots of sites that do run with their AFS cache on =
the shared root, so you'll probably be okay. Things just won't be quite =
as robust, or quite as speedy, as they might be.