>
> We are encountering a strange problem on our RS/6000's which may or may not
> be AFS related. Occasionally the X11 server stops dead for no apparent reason,
> even when the load average is low. The screen just freezes. The X
> executables and libraries are all in AFS.
>
> Word has it that another campus site which also has X living in AFS has been
> experiencing something similar recently. Has anyone else seen behavior like
> this?
>
I admit it, belong to that other Cornell campus site who has been having
similar problems with X and RS/6000s and AFS. We're currently running lots
of RS/6000 AFS clients, all at AFS 3.2, some at AIX 3.2.2, some at AIX 3.2.3E. After
months of X-server-freezing anguish, we may have finally narrowed down
what our problem may be (maybe).
Just like many sites, we try to put global things that may be updated
frequently (like /usr/lib/X11/app-defaults) in AFS to make sharing easier;
we also try to save local disk space by putting big parts of the system
which may not be heavily used off in AFSland, with a symlink on local client
disk to point to it. A good example always seemed to be /usr/lpp/X11/Xamples.
You don't really need all that stuff on local disk, do you? So when we
moved our RS/6000s from AIX 3.1.5 to AIX 3.2.2, we setup our Package
configuration files for most machines to point /usr/lpp/X11/Xamples off
into AFS. And lo and behold, we started seeing Xservers frequently freezing;
if you happened to telnet back into the machine in question to look around,
you would find no X-related processes (server or client) belonging to the
user who had been using the console running anymore.
Over time, we found we had machines with more local disk space, so we started
to leave more stuff on local disk. And the machines with all of their IBM-
shipped X pieces on local disk didn't seem to have the same problems with
X going to lunch as the machines with some of their X pieces off in AFSland.
Lots of things access other things in /usr/lpp/X11/app-defaults, but
why would anything care about what lives in /usr/lpp/X11/Xamples? Well,
look around in /usr/bin/X11, you'll find that many of the executables
there are just symlinks off to /usr/lpp/X11/Xamples/bin. Hmmm. I don't
know why X on RS/6000s should be so sensitive to having some pieces of
1 Xenvironment live on local disk and some live off in AFSland,
but our empirical observation seems to be that they're very sensitive.
Hope this is helpful; I don't pretend to understand it, but it seems to be true
for us... (besides, keeping up the voodoo quotient is always entertaining!).
--Judy
--
Judy Warren [EMAIL PROTECTED]
Cornell Theory Center (607) 254-8792
