Date: Fri, 8 Aug 1997 12:41:58 -0500 (CDT) From: Dave Bodenstab <imdave@mcs.net> To: questions@FreeBSD.org Subject: Strange disk geometry during install Message-ID: <199708081741.MAA04286@imdave.pr.mcs.net>
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I had to replace my boot disk (containing both dos and FreeBSD), so I bought a 4G drive to replace the previous 1.2G drive. I took the opportunity to do some experimentation. Previously, I had a primary & extended dos partition on the first 900 cylinders. FreeBSD used the remaining space -- I made the root slice reside entirely under cylinder 1024. All worked fine. Now, I noticed that my BIOS supported LBA, so I figured I might be able to boot from a partition beyond cylinder 1024. Here's what happened... can anyone explain it? On the totally clean disk I ran dos' fdisk. It reported total space of about 4G, and let me create partitions up to 2G. This I expected. I initially just created the partitions as they had been on the previous disk. I then ran FreeBSD's install [2.0.5... I know, I know... ;-( ] It of course worked as before. Next I decided to try putting FreeBSD in the first (large) partition, with dos at the end of the disk. I thought that with LBA support, I might get away with this. When I went back to dos' fdisk, it now reported only 504M total space !!! What's going on? Something happened during the FreeBSD install that has now confused dos. I know that the boot block for dos (not the master boot block) contains some bios disk parameters that dos picks up. But what could FreeBSD have done that changed this? The bios still is set to ``user'' disk type with geometry of 7752/16/63, this is what FreeBSD reports, but dos now thinks the disk has only 1024 cylinders !! What gives? Dave Bodenstab imdave@mcs.net
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