A big thank-you to Christian Weisgerber -- your ASCII-art diagrams explain the problem very clearly. (Otto Moerbeek's tweaks also help.) I think having these in the FAQ would be a great idea!
In parallel (i.e., at about the same time, but without yet having seen those messages), I decided to retry my partitioning sd0a at an offset of 128 sectors from the start of sd0c (instead of the default 64-sector offset I'd used previously). For reasons that are now clear to me after grokking naddy & otto's diagrams, this worked fine (zeroing the first megabyte no longer trashed the partition table). So I went ahead with setting up the softraid sd1 inside the newly-created sd0 partition: # cd /dev && sh MAKEDEV sd1 # bioctl -c C -r 144025 -l sd0a softraid0 # fdisk -i sd1 # install (select sd1, do a normal install) The installer warned me > The offsets used in the disklabel are ABSOLUTE, i.e. relative to the > start of the disk, NOT the start of the OpenBSD MBR partition. so I put sd1a at an offset of 256 sectors (I guess in hindsight 192 sectors would probably have sufficed, but wasting 64 sectors is trivial nowdays.) All is well, and I have a running 5.6 system. Yea! Question: Should the installer warning > The offsets used in the disklabel are ABSOLUTE, i.e. relative to the > start of the disk, NOT the start of the OpenBSD MBR partition. be added to the disklabel(8) man page and/or section 14 of the FAQ? I had a vague memory that I'd seen it somewhere, but I can't find it in either place. thanks again to everyone who contributed to this thread, -- -- "Jonathan Thornburg [remove -animal to reply]" <[email protected]> Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA "There was of course no way of knowing whether you were being watched at any given moment. How often, or on what system, the Thought Police plugged in on any individual wire was guesswork. It was even conceivable that they watched everybody all the time." -- George Orwell, "1984"
