Hello, On Sat, Jun 28, 2008 at 07:49:12AM +1000, Peter Jeremy wrote: > Yesterday, I planned to try an upgrade from 6.x to 7.x on one of the > servers at work, on the assumption that I could reasonably easily > revert to 6.x if things went bad. My confidence in being able to > do that was severely shaken when I saw "Upgrading metadata" messages > for both geom_mirror disks when the 7.x kernel booted. > > Whilst I did not need to revert, some examination of the geom_mirror > source shows that (as I feared), a 6.x kernel will choke on a 7.x > geom_mirror.
I didn't try now, but from my experience it should be fairly easy to
revert: Boot without gmirror from one the disks with the old kernel.
Have an old world available (CD, not yet installworld'ed) an write
gmirror label from single user mode with old metadata, add the other
disk and rebuild (more or less just go the way you go to setup a
bootable gmirror from an existing system).
You would be in more trouble if you had some kind of real RAID format
(like a RAID 5 or something) on the disk, but gmirror is basically a set
of metadata whilst any single disk of the mirror is actually in a
format, that can be used without gmirror.
I agree, that this is not actually straigt forward (as downgrading isn't
anyhow), but for the case "I see my 7.x kernel choking when upgrading
from 6.x to 7.x" it should still be easy enough for an experienced
admin.
Greetings,
Oliver
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