On Sun, Aug 04, 2013 at 06:24:33AM -0700, Chris Cappuccio wrote: > Erling Westenvik [[email protected]] wrote: > > > > physical disks: > > sd0a: 64 + N-64 > > sd1a: 64 + N-64 > > RAID 1 volume: > > sd2a: 64 + 64 + N-128 > > CRYPTO volume: > > sd3a: 64 + 64 + 64 + N-196 > > > > The space wasted on large disks is negligible but I would really like to > > know at which level the 64 sector offset may be set to 0. > > > > I believe the offset is for fdisk to store the MBR and first stage > boot loader. The BIOS uses it, OpenBSD does not. I bet you'll be ok > with a 0 offset on raid sd2a and sd3a (and only a disklabel, no > fdisk). The softraid manual shows using fdisk -i on the raid volumes, > and I hope that's just a mistake.
Thanks. My lack of knowledge about harddisk geometry, MBR's and disklabel partitioning is almost embarrasing and I'm sorry that I forgot to specify that the architecture is i386. It was the manpage for softraid that made me ask. As you state, it shows using fdisk -iy, something which confused me since I've seen examples of disklabels with both offsets of 0 and 64. I'll do some tests with different setups. Regards, Erling > The sparc/sparc64 platforms are good places to look because they don't > get touched by the BIOS (sounds like softraid) and therefore use don't > use fdisk, mbr, BIOS. (Some years ago someone gave me two Sun Sparc stations complete with 21" monitors, keyboard and everything. I'm ashamed to tell that I threw them away when moving house. It was before I got serious with OpenBSD..) > They're slso good because these platforms were designed ground-up to > run BSD, boots a fourth interpreter as its first program (OBP), and > know how to charge up the old boot blocks without compatibility glue > in-between. > > Here's a disklabel from my Sun Fire T1000. Unlike fdisk, no space > needs to be cut out for disklabel, which already owns the first 16 > sectors in the FFS layout. > > # /dev/rsd0c: > type: SCSI > disk: SCSI disk > label: ST31000524AS > duid: 6f7f7705c7253071 > flags: vendor > bytes/sector: 512 > sectors/track: 127 > tracks/cylinder: 16 > sectors/cylinder: 2032 > cylinders: 36366 > total sectors: 1953525168 > boundstart: 0 > boundend: 1953525168 > drivedata: 0 > > 16 partitions: > # size offset fstype [fsize bsize cpg] > a: 2099056 0 4.2BSD 2048 16384 1 # / > b: 17040352 2099056 swap # none > c: 1953525168 0 unused > d: 8390128 19139408 4.2BSD 2048 16384 1 # /tmp > e: 41420288 27529536 4.2BSD 2048 16384 1 # /var > f: 4196080 68949824 4.2BSD 2048 16384 1 # /usr > g: 2099056 73145904 4.2BSD 2048 16384 1 # /usr/X11R6 > h: 20972272 75244960 4.2BSD 2048 16384 1 # /usr/local > i: 4196080 96217232 4.2BSD 2048 16384 1 # /usr/src > j: 4196080 100413312 4.2BSD 2048 16384 1 # /usr/obj > k: 1848914768 104609392 4.2BSD 8192 65536 1 # /home
