Do we still need ATA disk CHS addressing?
Warner Losh
imp at bsdimp.com
Mon Aug 10 18:57:27 UTC 2009
From: Dag-Erling Smørgrav <des at des.no>
Subject: Re: Do we still need ATA disk CHS addressing?
Date: Mon, 10 Aug 2009 20:38:16 +0200
> "Julian H. Stacey" <jhs at berklix.com> writes:
> > Alexander Motin <mav at FreeBSD.org> writes:
> > > Have anybody seen ATA drive without LBA support in last years?
> > Yes
>
> Have you really, or did you just assume that "old" means "no LBA"?
>
> > I run 20+ assorted hosts from 4.11 to 7.2 Uni & Dual proc, i386 (real 386!)
> > to 686 & amd64 so I guess I'm
> > A) Pretty vulnerable to legacy scare.
> > B) A litmus tesst for a wider community of others, some with older kit,
> > not on lists or with bleeding edge latest hardware, but will
> > get hit when stuff eg HCS gets declared legacy=dumped.
>
> Do you seriously intend to run FreeBSD 9 on kit that is too old to
> support LBA? We're talking early nineties here. CHS doesn't scale past
> 504 MB, so any ATA disk larger than that must peforce support LBA. I
> bought my first 1 GB drive (Connor CFP1080) in 1995.
Is that also true in the pc98 realm? There's a number of weird
combinations there which use CHS addressing, but that's kinda forced
onto it by weird pc98 disk label format. I don't know if this is
required, and older stuff just won't work or not, but I do know that
there be dragons there. I know, at the very least, that the system
requires that the CHS geometry reported by the drive be faithfully
preserved. It is something we should ask nyan-san about at the very
least...
As for the 'are you seriously going to run FreeBSD 9 on them'
argument, there's a rather large number of systems that people said
would be too slow to run FreeBSD 7 or 8, yet they are running them
better than anticipated. They said that about many of the same
systems that Julian is running today.
My question, and maybe I missed this earlier in the thread, is what's
the benefit to removing this support? How much code is saved?
Having said all that, I think it is OK, but I'd definitely poll the
pc98 guys first... Just to make sure they don't need it and re-fork
the ata driver to get it :)
Warner
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