Path: utzoo!attcan!uunet!seismo!esosun!ucsdhub!loral!dml From: dml@loral.UUCP (Dave Lewis) Newsgroups: comp.sys.amiga Subject: Re: Request to Commodore (Bad Blocks) Summary: AAARRRGGGHHH!!! Keywords: trackdisk floppy format Message-ID: <1848@loral.UUCP> Date: 21 Sep 88 15:34:14 GMT References: <8891@cup.portal.com> <5660016@hpcvca.HP.COM> <4774@cbmvax.UUCP> Reply-To: dml@loral.UUCP (Dave Lewis) Followup-To: comp.sys.amiga Organization: Loral Instrumentation, San Diego Lines: 32 In article <4774@cbmvax.UUCP> ditto@cbmvax.UUCP (Michael "Ford" Ditto) writes: >In article <5660016@hpcvca.HP.COM> charles@hpcvca.HP.COM (Charles Brown) writes: >Also, your figures don't take into account that the 1.1 rotations of >trackdisk result in up to eleven sector I/Os ("up to" because I won't >assume that all the data on that track would be useful at that time), >while the index-synced method would take 1.5 rotations to read ONE sector. No, NO, NO!!!! He's said several times that the read operation would be identical; that only the writes would be aligned with the damn index mark like they should'a been all along! The read algorithm doesn't care where the track starts, it just finds the beginning and reads it. The real times, compared with the current (flaky) operations: (The way it is now = 1.0) Reads Writes Total (85% read, 15% write) ----- ------ --------------------------- 1.0 1.5 107.5 (7.5% longer) Writes currently take about 1 disk revolution. If ya have to wait for the index mark that adds 0.5 revolutions to the average write operation. Reads have to find the start-of-track NO MATTER HOW THE TRACK WAS WRITTEN, so aligning the tracks to the index will have NO EFFECT WHATSOEVER ON READ TIME! So we're putting up with wandering tracks (or musical sectors) for a measly 7.5% increase in floppy throughput. Even if you (unreasonably) assume 50% writes the difference is only 25%. This is a very small price to pay for increased reliability. -- Dave Lewis Loral Instrumentation San Diego (619) 282-3341 ihnp4 --\ bang --\ kontron -\ hp-sdd --\ calmasd ->-> crash ->--> loral!dml sdcrdcf -->--------> sdcsvax -/ (uucp)