This raid system is fully function and both hard drives are working perfectly. No power cable is included with this device.

The Buffalo DriveStation Duo 640GB RAID is a desktop external HDD with a storage capacity of 640GB, distributed across two 320GB WD Caviar Blue HDDs. It features a USB 3.0 interface for fast data transfer speeds and offers various useful features such as Buffalo's Backup Utility, SecureLock, and the ability to manage data with Buffalo Tools. The sleek black design, with dimensions of 8" x 5" x 3.5", makes it a convenient and reliable storage solution for your computer system.