Date: Wed, 15 Mar 95 20:21:21 MST From: terry@cs.weber.edu (Terry Lambert) To: phk@ref.tfs.com (Poul-Henning Kamp) Cc: rgrimes@gndrsh.aac.dev.com, current@FreeBSD.org Subject: Re: newfs: sectors per cylinder (4096) disagrees with disk label (36) Message-ID: <9503160321.AA16377@cs.weber.edu> In-Reply-To: <199503160250.SAA09150@ref.tfs.com> from "Poul-Henning Kamp" at Mar 15, 95 06:50:38 pm
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> > 1. Physical volume spanning. Like AIX, it is useful to have a > > logical partition on which you actually build your file system > > capable of spanning one or more phical partitions on one or > > more physical drives. > Is this an argument for or against ? An argument for seperation of geometry information from /dev accessable devices, but against seperation of them from device drivers. Basically, there need to be devices that access the raw disk (machine specific) which are used to access the DOS partitions from user space and to mount (using a clone) do partitions without a device being dedicated to the DOS partition. There also need to be devices that are for the logical partitions of the BSD DOS partition(s). These are for use by tools. These may also be accessable by clones. The tools are specific to the underlying partition maintenenace, which is machine specific. There finally need to be logical partitions that file systems are managed upon. These partitions don't know a thing about geometry. There need to be geometry "bleed through" "hints" to the upper layers. In the case of a non-translated MFM or ESDI device, ROTdelay still has meaning. The "perfection" of media (bad144, etc.) is handled at the middle layer, or in a layer between the middle layer and the first layer, depending on how machine specific this might get. > > 2. Ability to mount partitions using different physical layout > > strategies between machines running the same OS. Ie: a DEC > > Alpha Syquest disk on a 386 box. > > I'm lost, this has nothing to do with geometry in my book... Once > a filesystem is made, the geometry is determined isn't it ? It has to do with geometry, in that system specific geometry management (like a DOS partition table rendered in DOS geometry) must be used to get the file system offset. Specifically, removalble hard drive media could easily have a DOS partition table on it which a non-DOS aware box must have an intervening layer to deal with in or for the non-DOS aware box to mount the foreign media. I wasn't trying to raise a byteswap issue or anything. Terry Lambert terry@cs.weber.edu --- Any opinions in this posting are my own and not those of my present or previous employers.
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