Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!uw-beaver!uw-june!uw-entropy!uw-apl!grace!quick!srg From: srg@quick.COM (Spencer Garrett) Newsgroups: comp.arch Subject: Re: Why no disks with two HDAs ? Keywords: diskdrives, headdiskassemblies Message-ID: <234@quick.COM> Date: 22 Jun 88 08:25:35 GMT References: <2351@uklirb.UUCP> <2440@winchester.mips.COM> Organization: Quicksilver Engineering, Seattle Lines: 13 A big reason for not putting in two HDA's is that you would then have to align them. One big advantage of non-removable media is that as long as the heads don't move (WRT one another) it doesn't matter where they are. You just torque them down and format the drive. It is possible to get around this with embedded-servo information, but then changing heads requires a (short) seek, which does nasty things to filesystem throughput. (The cylinders get very small, equal to one track apiece.) It's a shame, too, because having multiple access arms could otherwise give you the best of both worlds (one big drive, for allocation efficiency and flexibility, versus several drives with the ability to seek independently).