Path: utzoo!attcan!uunet!samsung!zaphod.mps.ohio-state.edu!rpi!crdgw1!crdos1!davidsen From: davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) Newsgroups: comp.arch Subject: Re: disk rotation speed Message-ID: <2388@crdos1.crd.ge.COM> Date: 3 Aug 90 16:29:10 GMT References: <2635@mindlink.UUCP> <10048@pt.cs.cmu.edu> <1990Jul31.200043.5189@nlm.nih.gov> <1990Aug1.220440.20727@ico.isc.com> Reply-To: davidsen@crdos1.crd.ge.com (bill davidsen) Organization: GE Corp R&D Center, Schenectady NY Lines: 35 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? | Yeah, I know, you would have to either have two data paths to the | disk or one data path that was quick real quick and a buffer so that | you could keep both heads busy. First, you don't have to keep both heads busy. You can seek one while the other is busy, as many small systems do now with multiple disks, where there is a single data path from the controller to the main memory. The technology is pretty well in place, and seeks could be sent to the idle head while transfer was active, and to the closest head when no transfer was taking place. Second, I doubt that the electrical considerations are the problem. The form factor of disks has dropped from 14, to 8, to 5-1/4, to 3-1/2, to 2 inches (actually 5cm, the first metric disk). In those form factors you have a real problem with fitting a second actuator, and cooling it is also a problem. Some small disks specify a required aitflow as well as temperature now. You conclusions about the benefits are about right. It's not clear that the cost to benefit ratio will justify this feature at anything but the highest performance level right now. Having seen the change from the DSU10, 40 inch platters and 48MB capacity, to the 1.2GB showbox today, I think that the race for smaller may be about over, because the physical size of the drive is not much of a problem now (even at 3-1/2 inch). I predict that the next improvements will be in power and capacity, rather than just making drives tiny. -- bill davidsen (davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen) "Stupidity, like virtue, is its own reward" -me