I suppouse the storage space is connected to the computers by LAN.
All NAS has a OS on it, normally Linux on a RAID 5 array.

Although you see the drive as only one, in fact they are logical combination of all the drives. Splitting into two logical drives i think it will make it worst.
What is the brand and model of your drive space?
What is the RAID configuration (RAID 5)?
What is the E: space seen by the computers?