Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!usc!snorkelwacker!spdcc!esegue!johnl From: johnl@esegue.segue.boston.ma.us (John R. Levine) Newsgroups: comp.arch Subject: Re: disk rotation speed Message-ID: <1990Aug03.160144.3683@esegue.segue.boston.ma.us> Date: 3 Aug 90 16:01:44 GMT References: <2635@mindlink.UUCP> <10048@pt.cs.cmu.edu> <1990Jul31.200043.5189@nlm.nih.gov> <1990Aug1.220440.20727@ico.isc.com> Reply-To: johnl@esegue.segue.boston.ma.us (John R. Levine) Organization: Segue Software, Cambridge MA Lines: 22 In article wayne@dsndata.uucp (Wayne Schlitt) writes: >I have wondered about this for a long time. Are there many drives >with more than one actuators? Why arent there more? I gather it's a mechanical problem. You typically have one surface with servo tracks that the drive uses to align the heads. If there were two sets of disk arms, you'd have to ensure that the relative positions of the corresponding heads in each set were exactly the same. As it is, the relative positions don't matter so long as the positioning is repeatable. One way to avoid that problem would be to assign the two arms to different parts of the disk, e.g. the inside half and the outside half. You could put the arms on the same actuator, which gives you the effect of half as many cylinders each with twice as many tracks, or they could have separate actuators. I believe the first case is fairly common, I've seen Fujitsu disks that do that. The second I haven't seen, probably because by the time you have two actuators, you might as well build two separate drives. -- John R. Levine, Segue Software, POB 349, Cambridge MA 02238, +1 617 864 9650 johnl@esegue.segue.boston.ma.us, {ima|lotus|spdcc}!esegue!johnl Marlon Brando and Doris Day were born on the same day.