[OpenAFS] improving cache partition performance

Simon Wilkinson sxw@inf.ed.ac.uk
Mon, 29 Aug 2011 15:47:32 +0100

To paraphrase a famous AFS saying: The fastest disk access is the one =
you don't do.

If your disks are having performance issues (I'd also be interested in =
seeing utilisation figures, and the difference between the await and =
svctm times), then the easiest way to fix that is to have less requests =
hit the disks.

There are a few ways you can do this
a) Turn off journalling - you don't need a journalled file system for an =
AFS cache, and ext3 is known to be slower than ext2
b) Use a 1.6.0 AFS client. The Linux VM layer in the 1.6.0 codebase has =
been rewritten, so that we make much better use of the page cache, and =
satisfy more results from memory rather than going to the underlying =
c) Add more memory to your servers. Linux will use any free memory to =
cache disk data, so this can significantly reduce your IO overhead.