Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site rayssd.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!rayssd!jxc From: jxc@rayssd.UUCP (Jeffrey J. Clesius) Newsgroups: net.micro Subject: Re: Re: This is serious? Message-ID: <996@rayssd.UUCP> Date: Wed, 21-Aug-85 12:51:10 EDT Article-I.D.: rayssd.996 Posted: Wed Aug 21 12:51:10 1985 Date-Received: Sat, 24-Aug-85 15:04:02 EDT Sender: jxc@rayssd.UUCP (Jeffrey J. Clesius @ Raytheon Co., Portsmouth RI) Distribution: net Organization: Raytheon Co., Portsmouth RI Lines: 33 > 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. -- /^^^/ / __/__________________________________________________ / !/ Jeffrey Jay Clesius !\ / / Raytheon Submarine Signal Division !_\ /^^^/ / /! PO Box 360, Portsmouth, RI 02871 !/ / ^^^^ ! (401) 847-8000 (X4015) / / ! {allegra, decvax!brunix, linus, ccice5} rayssd!jxc /! / !____________________________________________________/_! / / / ^^^^