Date: Wed, 29 Mar 1995 19:33:09 +1000 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, gvrooij@mmra1.ms.philips.nl Cc: freebsd-bugs@freefall.cdrom.com, jkh@freefall.cdrom.com, pst@shockwave.com Subject: Re: kern/280: new slice manager totally confused about old slice disks Message-ID: <199503290933.TAA25301@godzilla.zeta.org.au>
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>> I think sysinstall creates a valid disk label with size >> #secpertrack * #heads * #cyl in both the d_secperunit and the 'd' partition >> size fields. The problem occurs when the sd driver blows away the 'd' >> partition size field (replacing it with the total #sec) without touching >> the d_secperunit field. The wd driver is more careful and verbose. It >Might well explain what we see indeed. But the same holds for the c partition. Maybe sysinstall set the size of the c partition correctly to extend to the end of the disk, and d_secperunit to match. Old versions of `disklabel -e' rounded down d_secperunit to a cylinder boundary so running `disklabel -e' could cause the problem. >But what abt the following scheme: >I've got a disk, labeled by 2.0R whit only one slice, namely for freebsd >with the defect I mentioned earlier (i.e. that the sd driver replaces >the c and d partition sizes with larger values than possible according >to the other drive params.). >I dont have sources handy and might well mix up the order of evaluation >but if the slice code rejects the c and d partitions because of their >sizes, it will also at least reject the (physically) last partition... The c partition size is rounded down while the d partition is rejected. These partitions are not used for normal operation (except maybe sector #2 of partition c to read the label) so normal operation is not normally affected. Similar rounding down of the a partition (e.g.) would cause problems if the file system extends into the lost sectors. Most such problems are avoided by specially handling the 50000-sector "whole disk for FreeBSD" partition table. Bruce
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