Two pools of the same length but different names won't log 'zfs upgrade -a' to both pools:
# zpool create -f f1 c1t1d0s6
# zpool create -f f3 c1t1d0s7
# zfs create -o version=1 f1/a
# zfs create -o version=1 f3/a
# zfs upgrade -a
# zpool history
History for 'f1':
2007-08-23.00:13:03 zpool create -f f1 c1t1d0s6
2007-08-23.00:13:05 zfs create -o version=1 f1/a
2007-08-23.00:13:09 zfs upgrade -a
History for 'f3':
2007-08-23.00:13:04 zpool create -f f3 c1t1d0s7
2007-08-23.00:13:05 zfs create -o version=1 f3/a
The function same_pool() has backwards logic for its strncmp() routine.
PS: its really cool that we can use 'set version' - makes testing life much easier!