Re: size of supervise/ !

> in case it matters: the filesystem format is jfs on a raid-1 device;

 supervise updates the "supervise/status" file everytime the service
goes up, or down, so this file accurately reflects the current state
of the service.
 A journaled filesystem will probably store every change in some way.
I suspect that the journalling of the status file has much to do with
the size of your supervise directory.

 Check your journals; clean them, if possible and appropriate.
 I generally suggest having supervise directories in a tmpfs (or
any other RAM filesystem).

-- 
 Laurent