Erling Westenvik [erling.westen...@gmail.com] 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. 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. 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
