On Dec 31, 2023, at 12:07 PM, Warner Losh wrote: > > Yes. Unlike today, the partitions covered the disk in different, overlapping > ways. And allowed for some parts of the disk to be uncovered by a > partition. You could then patch the offset and length into the kernel with > adb and use that area of the disk for swap space. > >> It was also helpful, if you had the drives, to nightly dd >> your real root to the "a" partition on another, identical >> drive, so that you could boot the backup root in an emergency. >> >> I don't remember for sure, but I think that Ultrix may have >> been the first BSD-style system to have disk labels, followed >> by some version of SunOS. All of that is way in the distant >> past though: mid- to late 80's. > > When I looked into it years ago, I convinced myself that SunOS > was the first to have it (since the very first version of SunOS 1.0 > had disk labels) and that all the other vendors followed suit within > a couple of years. Ultrix-11 had the fixed labels through its EOL. > I didn't see any disklable stuff in the Ultrix-32M that we have, but > it was admittedly a quick look. I wrote the first 2-3 HD drivers for Fortune Systems. I had the first one up and running[1] by late 1981. IIRC we used an ioctl to read/write sector 0 of a disk, which is where we stored partition info. I think by 1983 we were using some 4.1a bits (or at least influenced by it) so likely disklabel was used by then. The first disk drive was 5MB and cost $1700. But 5 1/4" disk capacities were growing fast so there was no question of hardwiring a disktab in source code. I even had a program that would try to "step" through cylinders until it ran into errors, to find at usable capacity! [1] Well, more like walking! Initially DMA didn't work on the first wirewrap boards so had to use PIO (programmed IO), at 25KB/s. A quick hack doubled that performance, while an ST506 disk could do 5Mbits/sec.