Hi. It seems you have to format the filesystem. More you have to label the new drive first. So the steps are:
fdisk /dev/<raid device>
press 'p' to print the data
press 'n' to create new partition
press 'w' to write the data to the harddrive
press 'q' to quit.
'h' stands for 'help' ;-)
The problem with fdisk is that it's rather user-unfriendly and (secondly) it can't create a partition larger than 2TB
There is a program called 'cfdisk' which acts like fdisk but has nicer user interface.
The only software I know that creates partitions larger than 2tb is 'parted' or 'gparted' for its gui version.
Now you have to format the partition.
For ext3 partition use:
mkfs.ext3 /dev/<partition device>
For jfs partition use:
mkfs.jfs /dev/<partition device>
ext3 is a standard partition format used in linux.
jfs is much more robust and has almost every feature that ext3 does. You may want to read about the differences, pros and cons. There are some articles on the web.
There is also xfs filesystem worth mentioning. It also performs better than ext3, especially in case of really large files.