You cannot re-format your N2100 with HFS+. You may use the HFSPLUS module to deal with HFS+ formatted USB drives. Be careful though, disable journaling if you intend to write to your HFS+ formatted drive (a limitiation of the linux driver). Best to also install META and enable automatic mounting of any USB drive.
So drives within the 2100 can only be formatted in NTFS? I bought my Thecus second hand with two drives already formatted inside - I presume since I can store files of bigger than 4GB that they must be NTFS. But if so, how come my Mac can read them with no problems or modifications?
You are thinking wrong. The file system of your N2100 is completely independend of the cllient os/file system. You use ext3 on your N2100, NTFS on Win and HFS on Mac and they can communitacte without probs.
Thats what samba and nfs do....
3* N2100 fw 2.1.09 with 512MB RAM, 500GB RAID1 and fanmod