[net.micro] This is serious?

binder@dosadi.DEC (No matter where you go, there you are.) (08/12/85)

Inertia rears its ugly head in yet another way.  I used to have access to a
MODCOMP III with the OS on a fixed-head disk.  We'd use the machine with no
trouble at all through the week, but the thing would invariably fail to boot
on Monday mornings.  One Friday someone got the bright idea to turn off the
disk, and Monday we ran it back up and the system booted fine.  We finally
figured out that the problem was inertia, in the guise of centrifugal force;
as long we we read and wrote things often enough, the bits didn't have time
to be thrown off the disk, but over the weekend was too long.  We had to
install a bit bucket under the disk drive to keep the computer room clean.

Cheers,
Dick Binder   (The Stainless Steel Rat)

UUCP:  { decvax, allegra, ucbvax... }!decwrl!dec-rhea!dec-dosadi!binder
ARPA:  binder%dosadi.DEC@decwrl.ARPA

jxc@rayssd.UUCP (Jeffrey J. Clesius) (08/21/85)

> Inertia rears its ugly head in yet another way.  I used to have access to a
> MODCOMP III with the OS on a fixed-head disk.  We'd use the machine with no
> trouble at all through the week, but the thing would invariably fail to boot
> on Monday mornings.  One Friday someone got the bright idea to turn off the
> disk, and Monday we ran it back up and the system booted fine.  We finally
> figured out that the problem was inertia, in the guise of centrifugal force;
> as long we we read and wrote things often enough, the bits didn't have time
> to be thrown off the disk, but over the weekend was too long.  We had to
> install a bit bucket under the disk drive to keep the computer room clean.
> 
> Cheers,
> Dick Binder   (The Stainless Steel Rat)

We had a similar problem whose solution worked to our advantage.  To avoid
the loss of bits off the edge of the disk, we installed a raised edge on the
circumference.  What we found was that the tracks were migrating over time
toward the outside of the disk.  Once we had installed a logarithmic track
seeking algorithm as part of the disk driver, we found that the capacity of
the disk was increasing steadily by about 10% per week.  The hardest part
about the track mapping algorithm was to allow for loss of migration while
the disk was not spinning due to downtime.

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