Date: Fri, 7 Aug 1998 03:14:02 +1000 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, mike@smith.net.au Cc: hardware@FreeBSD.ORG, ks@itp.ac.ru Subject: Re: IBM 16 GB IDE HDD Message-ID: <199808061714.DAA01632@godzilla.zeta.org.au>
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>> > 0x1000 Use LBA addressing instead of the default CHS addressing. >> >> This is seriously incomplete and out of date. LBA addressing should almost >> never be used, since no cases are known where it is necessary, and cases >> are known where it causes trashed disks (dumping to any drive where the >> default geometry is not the same as the fake LBA geometry). > >Which "default" geometry? Actually the current geometry (as possibly initialized by the BIOS). Several geometries are relevant here: a) The default geometry for the drive. b) The geometry initialized by the BIOS (possibly none, if the BIOS uses LBA mode and translates CHS for old interrupt interfaces to LBA). If no geometry is initialized, then the current geometry is prayerfully the default one. Recommended practice is to initialize it so that you don't have to pray. c) The hardware geometry initialized by FreeBSD. If the LBA driver flag is used, then I think a drive reset serves to initialize to geometry (a). Otherwise, geometry (a) is certainly initialized. d) The current geometry for the drive = geometry initialized by last OS or BIOS that initialized the geometry. e) The software geometry put into the in-core label for the whole disk. Same as (c) for the !LBA case; fake for the LBA case. Kernel dumps trash the disk if geometry (d) != geometry (e). >In a correctly configured system, geometry >is a nonissue. Not true. There are lots of booting and coexistence-with-improperly- configured-system issues. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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