How to add new hard drive w/ pre-existing data to Redhat 7

Have old disk w/ data to add to current configuration. Disk has been
recognized by hardware disk array. Currently have a 3 disk Raid 5
setup on pre-existing server running RH 7.2 (seawolf), disk I am
trying to add is recognized by Compaq server and is set up in raid
manager as single disk Raid 0.

when i do a df -k :

/dev/cciss/c0d0p1
etc...

I cannot mount anything in /dev/sda, b, c, d etc and the only thing it
will recognize is when I do a mount /dev/cciss/c0d1 /mnt/x.

Then it comes back w/ error msg:

VFS: Can't find a vliad MSDOS filesystem on dev 68:10
mount: you must specify the filesystem type


The new disk I am trying to add was part of a Raid 5, 5 Disk
configuration running RH7.

Any ideas? I am lost and it's 3am :)

thanks!

o.r.