From owner-freebsd-scsi@FreeBSD.ORG Fri Dec 17 12:17:31 2010 Return-Path: Delivered-To: freebsd-scsi@freebsd.org Received: by hub.freebsd.org (Postfix, from userid 1233) id B3DF51065672; Fri, 17 Dec 2010 12:17:31 +0000 (UTC) Date: Fri, 17 Dec 2010 12:17:31 +0000 From: Alexander Best To: Bruce Cran Message-ID: <20101217121731.GA29863@freebsd.org> References: <20101217115526.GA20772@freebsd.org> <20101217120955.00005f5a@unknown> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101217120955.00005f5a@unknown> Cc: freebsd-scsi@freebsd.org Subject: Re: "camcontrol identify ada0" and "diskinfo -v ada0" reporting different cylinders count X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 17 Dec 2010 12:17:31 -0000 On Fri Dec 17 10, Bruce Cran wrote: > On Fri, 17 Dec 2010 11:55:26 +0000 > Alexander Best wrote: > > > 484518 # Cylinders according to firmware. > > 16 # Heads according to firmware. > > 63 # Sectors according to firmware. > > ... > > cylinders 16383 > > heads 16 > > sectors/track 63 > > > > > > ...so how many cylinders does my hdd have? > > It almost certainly doesn't have 8 platters for a start, and neither > does it have 63 sectors per track. CHS is obsolete - the ATA-7 > specification has marked the fields as obsolete and all disks made in > the last 10 (maybe even 15?) years have used LBA. > > camcontrol displays what the disk reports via the IDENTIFY command > (I'm not sure if it's the "current" or default geometry it reports): > ATA says that disks larger than can be represented using CHS should > report having 16383 cylinders, which is needed for compatibility with > BIOSes. diskinfo just appears to take the size of the disk, > assume 16 heads and 63 sectors per track and put the rest into > cylinders. thanks for the explanation. > > There's another set of CHS values, and that's in geom: check for > "fwheads" and "fwsectors" in "gpart list". Geom name: ada0 state: OK fwheads: 16 fwsectors: 63 last: 488395021 first: 34 entries: 128 scheme: GPT > > See > http://lists.freebsd.org/pipermail/svn-src-head/2010-December/023134.html > for a (very!) detailed discussion of the various ways of calculating > CHS values. Unfortunately no decision was reached so it looks like > we're going to have a mismatch between camcontrol, diskinfo, geom, cam > and ata for a while yet. too bad. :( thanks for the link. i'll try to read through the entire thread, although i'm quite sure that the really techie details are too complicated for me to comprehend. > > -- > Bruce Cran -- a13x