Boot device question

[Chris Pratt]

I have a server with 6 hot-swap SATA slots. It was delivered
with the first slot empty and 5 drives set up as /dev/ad4 through
/dev/ad12. I'd never paid attention to this until I wanted to add
a 6th, now 4 years later. When I popped it in, I realized the
empty bay was not 6 but rather bay 1, and of course it wouldn't
boot. Presumably /dev/ad2 had now come alive for the first time.
I popped out the disk, rebooted and after it was up, I plugged it
back in (hot) and ran sysinstall. It didn't see the disk so I couldn't
fdisk it. No device files existed for it.

I was thinking a right approach would be to change fstab to
reference ad2 for all the system disk file systems, shutdown,
move that drive to the first bay and plug the new drive into the
2nd bay. This seemed like more of a permanent solution.
If those /dev/ad* files are created at boot dynamically,
this should work. I've found docs that imply that they are
dynamically discovered and created from FreeBSD 5 forward
(auto-discovery?). Are they or do I need to create them prior to
start up.

The thing is, there is no easy recovery from failure here since I
have no console monitor to let me see what's going on or to fix
fstab if it fails (counter-intuitively, the only place I can access
the console is from remote locations ;-)), so I just want to know
if I'm thinking straight? The plan is:

1. Change /etc/fstab entries for ad4 filesystems to ad2
2. Shutdown
3. Put the system disk in Bay 1
4. Power up

Should it boot?