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disks: Symbolics' can't handle power outage?

    Date: Thu, 27 Jun 1991 14:45 EDT
    From: bouma@cs.purdue.edu

    We seem to have a lot of trouble with disks on Symbolics' when the power
    goes out.  The last 3 times power went, a disk (or two) was corrupted each
    time.  We have Suns, SGIs, HPs plugged into the same lines, and NONE of 
    their disks were messed up, even though we have 10x more of them than Symb.

    What does it mean when it says "disk not ready on unit select".  After the
    last power outage we have a disk that always says that.  We have another
    that says that when you first turn the power on, but starts working again
    when you do a "reset".  Why would that be?  The most common problem is just
    bunches of sectors that can't be read.

    Bill <bouma@cs.purdue.edu>

We haven't had too much trouble with power outages; in fact, our Lisp
Machines frequently survived momentary drops that took down Vaxes.

If a disk is continuously not ready, I'd suspect that it failed its
self-test, or the controller board on the disk got screwed up by the
power failure.

One thing that could help in the future is if the disk has a
Local/Remote switch, set it to Remote.  This specifies that the disk
shouldn't spin up until it gets the appropriate command from the host.
In Local mode they'll spin up as soon as they get power (assuming their
Start switches are left on across the power failure).  Several disks
spinning up simultaneously can put a heavy load on the power line.  The
Lispm doesn't send the spin-up command until you hit its start switch.