Today, I did the upgrade from 3.0.99 to latest 4.1.17. The whole process worked smoothly, but my raid1 was missing from the file system after upgrading. After searching through the whole forum, I couldn't find a solution.
But, finally I figured it out and made it work.
if you have the same problem and when you execute command
and if you get
/dev/md0: ambivalent result (probably more filesystems on the device, use wipefs(8) to see more details)
you should run command (don't worry, this command will not harm any of your data)
if there are more than one offset looks like
offset type
----------------------------------------------------------------
0x3a37977f000 zfs_member [filesystem]
0x438 ext4 [filesystem]
you may created some other file systems on these disks (ZFS eg.)
for me, the second ( offset with 0x438 ) is the correct information I need. , so run command
this command will delete the correct meta information and create a backup for it. (locates in $(HOME) or /root, with filename wipefs-md0-0x00000438.bak)
then, erase all signature by running command
always remember to create a backup for the erased signatures.
finally, I restore the correct signature to the device with command
notice the seeking offset, which can be found from the name of the backup.
my raid1 storage comes back finally.