Not being exactly sure how to format the new disk, I visited the FreeBSD
documentation link suggested by the Diary's vinum page and read the
details on how to create a "dangerously dedicated" (the original drives
on the plex were sliced by sysinstall) disk. Once that was done, all I
had to do was change
/etc/vinum.conf to this:
drive drive1 device /dev/ad4s1e
drive drive2 device /dev/ad6s1e
drive drive3 device /dev/ad0e
plex org concat
sd length 29314m drive drive1
sd length 29314m drive drive2
sd length 78355m drive drive3
Then I rebooted the system to single user mode, and did this:
# vinum resetconfig
Type 'NO FUTURE' as is necessary. This will destroy the previous
configuration on the vinum volume.
# vinum create -f /etc/vinum.conf
[..some vinum output..]
# growfs /dev/vinum/firepipe
Growfs(8) will ask whether the filesystem is backed up.
NOTE: Backing up the filesystem is HIGHLY recommended. I did this
*BEFORE* touching the new drive or the RAID filesystem.
Growfs(8) will then proceed to extend the filesystem and it will give an
output similar to newfs(8), in that it prints the locations of the
superblocks. Note, however, that these are *new* superblocks on the
filesystem, as they are being placed on the *new* drive. Once this
process finishes, the system should be able to mount the filesystem with
the additional disk space.