Disk Hanging Interruptions

[Barry Margolin <barmar@THINK.COM>]

    Date: Mon, 4 Dec 89 12:22:46 EST
    From: MALKIN@ibm.com

    I'm the system administrator for a network of 3605's, 3640's, 3670's
    and a 3620.  Every so often (~once a week) our file server (one of
    the 3670's) hangs and crashes into the FEP command mode with the
    error:

	  Disk Hung, did not respond for 60 seconds.

    Usually, all I have to do to get back into the regular command mode is
    to execute "continue" at the FEP prompt.  Even though the recovery is
    simple, these interruptions are ever so irritating since whenever this
    error occurs, no one can access the main file system.  Anyone have any
    thoughts on avoiding these interruptions?

	  Peter Malkin, malkin@ibm.com

I've seen this happen with 3640's with 368MB disks, and know the cause
of it in that case, but I don't know why it would happen to a 3670.  In
the case of the 3640, the problem is that sometimes the disks are
configured to run an exerciser when they are idle; the Lispm, however,
expects the disk head to be where it left it, while the exerciser can
leave the head at another track.

                                                barmar