A couple quick notes I tossed up on the tech blog:
http://techblog.wikimedia.org/2009/07/intermittent-media-server-load-proble…
Domas thinks it's related to this problem with ZFS snapshots badly
affecting NFS server performance in some cases:
http://www.opensolaris.org/jive/thread.jspa?messageID=64379
Actual load from clients doesn't seem problematic, but the NFS horror
can cause things to time out badly, which sometimes affects the main
apaches as well as the image scalers. (Especially when, say, deleting a
category of 100 image pages. :)
We've got it behaving reasonably well at the moment, but we'll want to
keep an eye on things until we've reduced the coupling between things a
bit...
-- brion