8.4 Data Not Compatible with 9.0.1 Upgrade?

I did an upgrade on my database server this past weekend and the
database fails to start. I checked /var/log/postgresql and found the
reason:

[root@slave ~]# ps aux | grep postgres
root      5189  0.0  0.0   8128   956 pts/0    S+   12:28   0:00 grep postgres

[root@slave ~]# /etc/rc.d/postgresql start
:: Starting PostgreSQL

                  [BUSY] server starting


                  [DONE]
[root@slave ~]# ps aux | grep postgres
root      5205  0.0  0.0   8128   960 pts/0    R+   12:28   0:00 grep postgres

[root@slave ~]# tail -n 50 /var/log/postgresql.log
FATAL:  database files are incompatible with server
DETAIL:  The data directory was initialized by PostgreSQL version 8.4,
which is not compatible with this version 9.0.1.
FATAL:  database files are incompatible with server
DETAIL:  The data directory was initialized by PostgreSQL version 8.4,
which is not compatible with this version 9.0.1.
FATAL:  database files are incompatible with server
DETAIL:  The data directory was initialized by PostgreSQL version 8.4,
which is not compatible with this version 9.0.1.

Does anyone know if this is a issue with PostgreSQL or with the way
Arch Linux packages the upgrade?