Asus PCI-DA2200 - Manual (Page 296)

ASUS GUI RAID Manager: Array Management
4.16 Dynamic Logical Drive Expansion 4-45
From the menu, select Partition Logical Drive. You will see
that the 1800MB logical drive is composed of two 900MB
partitions.
Follow the directions in section 4.13 to map the new
partition to a Host LUN. The new partition must be
mapped to a host LUN in order for the HBA (host-bus
adapter) to see it. Once you have mapped the partition,
reboot Windows NT. The HBA should be able to detect an
additional "disk."
Return to Windows NT Server’s Disk Administrator. There
now exists a Disk 2 with 900MB of free space. Click on
Disk 2 to select it.