On Fri, 16 Dec 2005 22:14:34 +0000, Jason McIntyre <[EMAIL PROTECTED]> wrote:
>On Fri, Dec 16, 2005 at 01:50:48PM -0800, J.C. Roberts wrote: >> >> (2) When doing the installation disklabel, the "suggested" starting >> offset for the 'a' partition is 0? I know using an offset of 0 is >> discouraged on i386 and other systems (default is 63), so I figured I'd >> ask if using a 0 offset is the "best/correct" way for alpha? >> > >i'm going to let nick answer this (you're reading, right nick? ;) >*i* don't know, but i'd like to know the answer. > >faq 14.10 says, at one point: "Notice that the offset starts at 63. This >is what you want." > >i'm trying to find where we document *why* 63 is "what you want" and if >it's MI. > >jmc Hi-ya jmc, It is documented in http://www.openbsd.org/faq/faq4.html [QUOTE] It is important that the first partition skips the first track of the disk, in this case, starting on sector 63. This will vary from machine to machine and disk system to disk system. If an OpenBSD partition is created starting at offset 0, this partition table will end up being overwritten by the OpenBSD partition's Partition Boot Record. The system may still be bootable, but it will be very difficult to maintain, and this configuration is not recommended or supported. [/QUOTE] The trouble is faq4 is very x86-centric. Though the disks (seagate) and controllers (qlogic) on *this* particular alpha are also usable on x86, we're still talking about a vastly different architecture. On an alpha there may not be a need for a "Partition Boot Record" per se because it's all handled by the system firmware (the SRM Console). As long as the disk holds a file system known by the SRM (i.e. CD9660, FAT or FFS), booting a kernel from a chunk of media is very straight forward. JCR
