Path: utzoo!mnetor!uunet!husc6!mailrus!ames!hc!beta!unm-la!unmvax!turing.UNM.EDU!mike From: mike@turing.UNM.EDU (Michael I. Bushnell) Newsgroups: comp.unix.wizards Subject: Re: Cylinder boundaries in 4.3BSD Message-ID: <971@unmvax.unm.edu> Date: 20 Apr 88 02:52:20 GMT References: <8808@eddie.MIT.EDU> <947@unmvax.unm.edu> <8843@eddie.MIT.EDU> Sender: news@unmvax.unm.edu Reply-To: mike@turing.UNM.EDU.UUCP (Michael I. Bushnell) Organization: University of New Mexico, Albuquerque Lines: 47 In article <8843@eddie.MIT.EDU> nessus@athena.mit.edu (Doug Alan) writes: >> What we do is make the disk look like an RA-81 or an RD-51. >That will work, but you still have the problem that your partitions >are not beginning at the beginning of cylinders. This messes up the >Berkeley Fast File System's perfomance fine-tuning. That isn't too critical. If a partition starts half-way through a cylinder, the first cylinder group of the second partition and the last cylinder group of the first partition will still be "close" on the disk to themselves. The /etc/disktab entries are correct for the particular disk used, and so the cylinder groups are allocated at the right places. >> If you make it look like an RD53, then you will still need the >> special disktab entry, but you won't have the benifit of separate h >> and g partitions. >I understand, but I don't want separate g and h partitions anyway, so >this is not a problem. >> Yet another possibility, if you don't really care about getting >> "standard" kernels to run on them, is to make it look like an rd51. >> rd51 is the type the controller returns if it can't determine the >> type. That is what we do for almost all our large microvax disks. >If I don't care about getting standard kernals to run on them, I'd >just use my own customized partition table, and then I'd get the >fine-tuning right. The question is how much will using a standard >partition table, which has not been customized for a nonstandard >drive, degrade system performance? One percent? Then, who cares. >Fifty percent? Then, it's worth caring about. It doesn't damage things that much. The performace disadvantages are NIL. What you MUST do is have a custom /etc/disktab entry for the disk. N u m q u a m G l o r i a D e o Michael I. Bushnell HASA - "A" division 14308 Skyline Rd NE Computer Science Dept. Albuquerque, NM 87123 OR Farris Engineering Ctr. OR University of New Mexico mike@turing.unm.edu Albuquerque, NM 87131 {ucbvax,gatech}!unmvax!turing.unm.edu!mike