Re: 'Floating point exception'

   From: Thomas Michael Hagen <[email protected]>

   > Bill Yerazunis wrote:
   >
   >> We schemed on that quite a bit, but the killer was that statistics
   >> files on NFS servers _cannot_ be safely locked within the NFS
   >> semantics.
   >
   > Not trivial, yes, but mail systems have been reliably locking
   > mailboxes placed on NFS storage for ages.

Near as I can figure out, they're not.  There's a higher level server
operating on the mailserver hosts acting as a lock manager.

The killer is that NFS semantics allow clients to cache files _locally_,
and not even inform the server that those files exist until it's
"convenient" to do so.  Usually that's quick, but sometimes not.

So, creating a lock file, twiddling for 10 milliseconds, and then
deleting the lock file is only guaranteed visible on the local host.
It may or may not ever be propagate in that 10 msec to the server, 
let alone to any other client machine.

That's the problem that nobody seems to have fixed.

       - Bill Yerazunis

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