Gtar restore on 5.1a

["Malli, Brandon" <brandon.malli@xxxxxxxxxxxxx>]

Managers,

We typically use a script (that basically invokes a gtar) to create
backups of all our 4.0x hosts.  Once the gtar of each filesystem has
been created we simply transfer it to the new host - which is booted off
cd with the drives mounted to a temp directory - untar the filesystems
to the appropriate mount point, fix the host specific files (/etc/fdmns
links, fstab, etc), reboot, rebuild the kernel, reboot again and voila.
The new host comes up just fine. 

When we try to use this procedure on 5.1a I get a "panic (cpu 0):
init_rootdev: boot device translation failed" error and consequently am
unable to boot - even with single user.  As I recall 5.1a manages the
disk drives differently and the procedure we use on 4.0x should not
work.  What I'm looking for is a brief technical explanation why and a
suggestion as to what we might use for a simple backup solution similar
to the 4.0x procedure.

Not a urgent matter but one I would greatly appreciate any advice on.

Thanks in advance,

Brandon Malli