Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!decvax!wivax!cadmus!harvard!seismo!hao!hplabs!sri-unix!lou@AEROSPACE.ARPA From: lou@AEROSPACE.ARPA Newsgroups: net.unix-wizards Subject: Re: 'mkfs(1m)' for RA81s - gap? Message-ID: <12806@sri-arpa.UUCP> Date: Mon, 8-Oct-84 11:37:50 EDT Article-I.D.: sri-arpa.12806 Posted: Mon Oct 8 11:37:50 1984 Date-Received: Thu, 11-Oct-84 04:21:47 EDT Lines: 37 From: Lou Nelson>Return-Path: >Date: 6 Oct 84 5:13:30-PDT (Sat) >To: Unix-Wizards@BRL-VGR.ARPA >From: ihnp4!houxm!garys@UCB-VAX.ARPA >Subject: 'mkfs(1m)' for RA81s - gap? > >Article-I.D.: houxm.926 > >Several sources have come up with varying opinions about the optimal >Gap Size and Blocks/cylinder for DECs RA81 drives. We're under the >assumption of 728 Blocks per cylinder (14 R/W heads x 52 sectors/track). > >If 728 is correct, what should the proper gap size be considering >3600 RPM? > >Thanks in advance. > >Gary Seubert - HOCC >[..ihnp4!]houxm!garys > >(running System V if it makes a difference) I'm not really a wizard, but here goes anyway. It does make a difference that you are running System V, since unlike 4BSD I think only 1 block is read in at a time. So your 728 is probably correct. The "gap size" is the important number however and, using a program posted by mh3bs!agp on 11/19/83 (who in turn got it from a USENIX paper), I measured 9 as the value that gave the best performance on my RA81s before I kicked them out the door in favor of Eagles. If you wish, assuming this reaches you, I can send you my modification of that program that includes RA81s and Eagles and you can run some experiments to determine which numbers are best for your configuration. Regards, Lou