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Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!elroy.jpl.nasa.gov!sdd.hp.com!math.ohio-state.edu!cs.utexas.edu!uunet!mcsun!news.funet.fi!klaava!klaava!not-for-mail From: torvalds@klaava.Helsinki.FI (Linus Torvalds) Newsgroups: comp.os.386bsd.development Subject: Re: Hard disk geometry translation (was V86 mode ...) Date: 13 Aug 1993 23:21:02 +0300 Organization: University of Helsinki Lines: 36 Message-ID: <24gt3e$gg7@klaava.Helsinki.FI> References: <107725@hydra.gatech.EDU> <1993Aug9.224939.19834@fcom.cc.utah.edu> <24cc1hINNo8@kralizec.zeta.org.au> <CBo9C6.9ED@sugar.neosoft.com> NNTP-Posting-Host: klaava.helsinki.fi In article <CBo9C6.9ED@sugar.neosoft.com> peter@NeoSoft.com (Peter da Silva) writes: >In article <24cc1hINNo8@kralizec.zeta.org.au> bde@kralizec.zeta.org.au (Bruce Evans) writes: >> Linux just uses the translation given by the BIOS. The only problem >> with this is is that the translated geometry may not be appropriate >> for file system layout optimizations. > >Worse, you could lose disk space. For example, the translation given by the >Compaq BIOS eats between 30 and 60 MB off the drives I use. This is usually not a problem on most systems: almost all BIOSes have a "type 47" or whatever that allows you to set your geometry to suit your taste. Linux uses the BIOS values for several reasons: - it's easier. 'nuff said. The "drive translation problem" subject has never even come up in the linux camp as far as I know, but I seem to see it every now and then in the 386bsd groups. - less problems with sharing the disk with other systems: the partition table makes more sense if everybody agrees on the layout of the disk. - I personally think the "translation overhead" mentioned by some folks as a source of inefficiency for the filesystems (either due to the controller getting slower due to translation or due to the fs not knowing about the real geometry) is mostly a load of bull-sh*t. It may have made sense 10-20 years ago, but I doubt the FFS disk geometry optimizations are really worth it these days with controllers that do sector mapping etc (the BSD 4kB blocks are probably a *much* larger win when compared to linux' 1kB blocks). - parly the same as the above: new drives usually have a variable number of sectors anyway in reality, so trying to use a "native mapping" is definitely not worth it. Let the hardware sort it out: no need to worry unnecessarily on a software level. Not to mention the fact that it's ugly in the extreme that the filesystem should need to know anything about the geometry in the first place. Personal opinions, not backed by numbers.. Flame me all you dare, Linus