Replacing broken drive on RocketRaid 1520 SATA RAID controller

[N3TW4LK3R]

hi,

I'm running 5.4-RELEASE on a server with a Highpoint RocketRAID 1520
controller. Recently one of the drives failed, but the system kept running,
which is nice.
Now, however, I'm trying to replace the drive with a new (almost identical)
one:

after plugging in the drive:

# atacontrol status ar0
ar0: ATA RAID1 subdisks: ad4 status: DEGRADED

ok, that's normal

# atacontrol list
ATA channel 0:
    Master:      no device present
    Slave:       no device present
ATA channel 1:
    Master:      no device present
    Slave:       no device present
ATA channel 2:
    Master:  ad4 <Maxtor 6L160M0/BANC1E00> Serial ATA v1.0
    Slave:       no device present
ATA channel 3:
    Master:  ad6 <Maxtor 6L160M0/BANC1E50> Serial ATA v1.0
    Slave:       no device present

Nice, so the drive is properly connected.

# atacontrol addspare ar0 ad6
atacontrol: ioctl(ATARAIDADDSPARE): Device not configured

damn :(

I read here:
http://lists.freebsd.org/pipermail/freebsd-current/2004-October/041896.html
that i should try # atacontrol addspare 0 ad6 but the result is identical :(

I also tried attaching and detaching ad6, overwriting the first blocks of
the drive with zero's, without success.

any ideas?