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Received: by minnie.vk1xwt.ampr.org with NNTP id AA5177 ; Tue, 22 Dec 92 07:00:54 EST Path: sserve!manuel.anu.edu.au!munnari.oz.au!sgiblab!zaphod.mps.ohio-state.edu!cs.utexas.edu!uunet!pipex!warwick!uknet!gdt!aber!fronta.aber.ac.uk!pcg From: pcg@aber.ac.uk (Piercarlo Grandi) Newsgroups: comp.unix.bsd Subject: Re: [386BSD] Disklabel for MAXTOR LXT340S Message-ID: <PCG.92Dec18223754@decb.aber.ac.uk> Date: 18 Dec 92 22:37:54 GMT References: <1992Dec10.080231.10747@email.tuwien.ac.at> <1992Dec12.100620.16224@tfs.com> <1992Dec15.165013.18162@prism.poly.edu> Sender: news@aber.ac.uk (USENET news service) Reply-To: pcg@aber.ac.uk (Piercarlo Grandi) Organization: Prifysgol Cymru, Aberystwyth Lines: 50 In-Reply-To: kapela@prism.poly.edu's message of 15 Dec 92 16: 50:13 GMT Nntp-Posting-Host: decb.aber.ac.uk On 15 Dec 92 16:50:13 GMT, kapela@prism.poly.edu (Theodore S. Kapela) said: (Martin BIRGMEIER) writes: Martin> Hello netters, Martin> MAXTOR LXT340S 6.20 Martin> cylinders: 324 <=========================== (!) kapela> (Julian Elischer) writes: Julian> It used the BIOS's idea of the geometry which is different. Julian> (The adaptec sets it up to LOOK LIKE 32sec, 64heads, 324CYL) in Julian> fact since the disk MAY have Zone recording we may BOTH be Julian> wrong! kapela> YES! The drive *DOES* use Zone-Bit Recording (I have the IDE kapela> version [ an LXT-340A ] that I am temporarily using for 386bsd. Confirmed. Actually recent SCSI/IDE disk drives are not disk drives at all. They are fairly powerful minicomputers (the LCT340 has got a 68000 with 256KB of RAM, quite a bit of ROM, and the operating system that runs on it keeps overlays in the last cylinders of the disk itself) dedicated to driving a disk drive. The LXT340 is just a disk server, only it uses the SCSI protcol over a SCSI bus rather than say NFS over an Ethernet bus. The OS that runs on the minicomputer does a lot of nifty tricks, just like a file server would do; caching, read ahead, error recovery and so on. In practice it is impossible to treat it as a disk drive. Therefore the best bet is to give a bogus geometry, of which the default Adaptec supplied one is one of the most convenient, being N cylinders of 1MB each, which makes partitioning easier, and abandon all hopes of doing lowe level optimizations as those done in the BSD filesystem code, that try to minimize things like rotational latency, which are actually handled by the LXT340 OS. A couple of years ago we had a discussion on this; somebody recently posted in this newsgroup a patch along the line sof that discussion that just makes the BSD filesystem code try to keep block sequentially contiguous if the parameters indicate it is a SCSI disk, with no fancier layout policy (which are of dubious value anyhow). -- Piercarlo Grandi, Dept of CS, PC/UW@Aberystwyth <pcg@aber.ac.uk> E l'italiano cantava, cantava. E le sue disperate invocazioni giunsero alle orecchie del suo divino protettore, il dio della barzelletta