From owner-freebsd-current Wed May 24 11:15:32 1995 Return-Path: current-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id LAA19519 for current-outgoing; Wed, 24 May 1995 11:15:32 -0700 Received: from cs.weber.edu (cs.weber.edu [137.190.16.16]) by freefall.cdrom.com (8.6.10/8.6.6) with SMTP id LAA19513 for ; Wed, 24 May 1995 11:15:28 -0700 Received: by cs.weber.edu (4.1/SMI-4.1.1) id AA08459; Wed, 24 May 95 12:07:26 MDT From: terry@cs.weber.edu (Terry Lambert) Message-Id: <9505241807.AA08459@cs.weber.edu> Subject: Re: newfs weirdness... To: pb@fasterix.freenix.fr (Pierre Beyssac) Date: Wed, 24 May 95 12:07:26 MDT Cc: freebsd-current@freefall.cdrom.com In-Reply-To: <199505240059.CAA12436@fasterix.frmug.fr.net> from "Pierre Beyssac" at May 24, 95 02:59:51 am X-Mailer: ELM [version 2.4dev PL52] Sender: current-owner@FreeBSD.org Precedence: bulk > newfs doesn't seem to use the number of sectors by cylinder it gets > from the disklabel. It correctly warns that it will use 4096 and that > it differs from the disklabel value, though. > > Is that the expected behaviour ? Yes; modern SCSI drives use ZBR (Zone Boundry Recording), which means that the geometry is translated. Since it's in hardware (it can be recovered using SCSI II commands only), it's largely irrelevent to most operations; however, the head seek and rotational latencies are then wrong in UFS/FFS everywhere except near the fron of the disk, and even then they could be shifted. The result is that UFS/FFS optimizations for linearly laid out disks (ESDI/MFM/RLL) are actually causing slower performance by expecting seeks when there are non, etc. the 4096/1 geometry is a way of "shutting off" most of the UFS/FFS optimizations. If you are using a non-ZBR disk, you can overrride the 4096/1 with a parameter to newfs. Note: I'm not sure if it uses the BIOS fictional geometry (which would have the same deleterious effects as a ZBR geometry), or if it uses the one reported by the controller when you do the override. This should probably be investigated. Terry Lambert terry@cs.weber.edu --- Any opinions in this posting are my own and not those of my present or previous employers.