Date: Tue, 26 Nov 1996 15:13:05 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: bde@zeta.org.au (Bruce Evans) Cc: bde@zeta.org.au, terry@lambert.org, current@freefall.freebsd.org, darrylo@sr.hp.com, jkh@time.cdrom.com, rgrimes@GndRsh.aac.dev.com Subject: Re: 2.2-ALPHA install failure Message-ID: <199611262213.PAA25659@phaeton.artisoft.com> In-Reply-To: <199611262202.JAA21885@godzilla.zeta.org.au> from "Bruce Evans" at Nov 27, 96 09:02:22 am
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> >If you are going to present fake geometry numbers, they should percoalte > >up from where the real geometry numbers are coming from. > > They do percolate up, but there is no "real" geometry. There lots of > different geometries: > > default for newfs: independent, X/1/4096 > values in the label: independent, usually unused > values in the partition table: should agree with BIOS > BIOS indepependent, important only for booting and > in other OS's > physical: independent, usually an average for sectors/ > track, usually unused > > These geometries should NOT be visible in all layers. Oh, I agree. Anything other than the "DOS PRIMARY PARTITIONING" or "DOS EXTENDED PARTITIONING" layers could care less: they deal strictly with sectors. The layer itself would make the geometry-to-sector-start+length translation. All subsequent layers wouldn't care, unless they were also geometry sensitive (say Partition #1 in the example I posted was a "DOS EXTENDED PARTITIONING" instead of "none"; it would care). The point is that as long as it can get an absolute sector start and length (for a linear run) or an absolute sector start and a "length" that represents the total number of sectors in the run, and a function to take a linear offset within the run and translate it to a physical sector, then the upper layer only cares about some sector number 0-N. All the FS cares about is that it has N sectors, and heres a device where they can be linearly accessed. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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