Date: Wed, 16 Sep 1998 09:04:31 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Mike Smith <mike@smith.net.au> Cc: joelh@gnu.org, Terry Lambert <tlambert@primenet.com>, tom@uniserve.com, gpalmer@FreeBSD.ORG, irc@cooltime.simplenet.com, freebsd-current@FreeBSD.ORG Subject: Re: Download of FreeBSD 3.0-SNAP Message-ID: <3217.905929471@critter.freebsd.dk> In-Reply-To: Your message of "Tue, 15 Sep 1998 15:58:51 PDT." <199809152258.PAA01641@dingo.cdrom.com>
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In message <199809152258.PAA01641@dingo.cdrom.com>, Mike Smith writes: >> Without knowing the true geometry of the disk (which I assume EIDE >> doesn't allow), we can't optimize for the cylinder patterns anyway, so >> I suppose it's a moot issue. I suppose that by manually specifying >> the geometry at format time then it could be slightly optimized for >> those hdd's that come with true geometry. Was that taken out because >> the computation was outweighing the seek time benefits, or what? > >Disk geometry is nonlinear, and the calculations involved in optimising >for it are complex and not really compatible with the optimisations for >this sort of thing already part of the filesystem. ... Which have been disabled since 2.0.5 or something, we're now running on a pseudo geometry which fails horribly on huge disks. According to Kirk, 16 to 32 is the right number of cylinder groups, all over 50 is waste. we can end up with 200+ cgs on modern disks :-( >There's no such thing as "true geometry" anymore. Well, there is, but we'd like to avoid having to deal with it. -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." "ttyv0" -- What UNIX calls a $20K state-of-the-art, 3D, hi-res color terminal To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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