This is a long one, so settle in.
It started with a seemingly stable ubuntu 6.06 lts server install with 5.0.8 OSS zimbra running smooth (for the most part). (note: two symmetrical 400gb drives in an mdadm RAID 1 config)
we wanted to up from 6.06 to 8.04 to get better resource management and stay current. The plan of attack was 6.06 -> 8.04 first, then reboot and run 5.0.8 -> 5.0.11.
I ran ubuntu update from update-manager and it seemed to go smooth. Other than a warning about removing some unused unneeded packages there were no outstanding concerns.
Upgrade completed and it prompted for a reboot. On reboot it froze. After a hard restart it dropped to a busybox prompt in the initramfs. I wasn't able to do anything. Couldnt mount, coulnt read, half the commands weren't working, nothing.
So after much panicing, and trying to boot to the second RAID drive along with a slew of other attempts - no dice. No matter what we tried (recruited a friend who's a linux guru) always back to the busybox prompt.
New plan: format one of the RAID drives with a new install of 8.04 and pull the data over. No dice, couldn't mount the second drive. (kept getting error "unknown file system") basically mdadm was barfing and din't know what to do. We even tried manually mounting the partition... nothing.
We did manage to use grub to boot to the other drive once, but it appeared to be corrupted and fsck threw a bazillion errors and quit after a while. Even e2fsck with a backup superblock did no good.
New plan #2: reformat one of the drives AGAIN with 6.06 and rebuild from backup to get back to square one.
Install went smooth, reinstalled 5.0.8 -s, rsynced to latest /opt/zimbra backup, zmfixperms, and then upgrade with 5.0.8 install.sh.
FAILED. every time on the mysql logger. So I hopped on AIM and hunted down mmorse from the zimbra team (that guy deserves a medal). who late on a sunday was very gracious and helpful and walked me through deleting and rebuilding the logger. but still getting the same fail on install.
more to come with details of what we tried: