On Sun, 9 Jul 2023 at 17:41, Izumi Tsutsui <tsut...@ceres.dti.ne.jp> wrote: > > > I was using fdisk to setup a USB key on NetBSD-10 and noticed its > > still defaulting to 63 sector offset, including when "1m" is entered: > > fdisk(8) man says: > > -A ptn_alignment[/ptn_0_offset] > [..] > > > > If > > the first partition is not defined then the alignment and > > offset > > for disks larger than 128GB is set to 2048 (1MB).
Aha, thanks! I can understand why 128GB was picked - as it's the ~largest theoretically non-LBA accessible ATA size. However, given than ATA-1, which maxed out at 2GB supported LBA, and the earliest x86 machine NetBSD now supports is a 486, I suspect the set of ATA/IDE machines that NetBSD supports that do not support LBA is very small, and the set which do not support LBA but can take >2GB drives is close to (if not) empty. In practice I think it would be better not to penalise current use of "small" (120GB SSD or 64GB or or CF/USB devices) for an edge case of older hardware (note this is coming from someone with a NetBSD/vax system :). If someone has a ST506/412 device somewhere, or a genuinely ancient ATA drive then we could retain the current behaviour for small (<=2GB) drives, but I think for at least >2GB we should default to 2048 sector alignment David
