We started experiencing AFP problems and general instability on one ofour Mac OS X servers today. AFP locked up and sucked a lot of resources, caused some bogus error messages in the logs. Kept getting this in particular:

AppleFileServer[4806] MDSChannelPeerCreate: (os/kern) invalid argument

It looks like this may be due to a permissions problem on one of the root drives our AFP server is making available to clients. Looking at the files within the .fseventsd directory on the drive’s mount point, I noticed that everything beneath .fseventsd was owned by root:unknown. Recursively chown’ing this to root:staff and setting permissions to 770 seems to have stopped the errors and returned stability after restarting AFP.

This was one of those problems that Googling didn’t yield a good answer to initially. I really had to dig and though I’d post this up for others to see. Make sure you post a comment if this helped you.