Secure your vital data with WD's My Book Mirror Edition dual-drive storage system with RAID Mirroring. With RAID-based continuous data protection, automatic data backup software, and user-serviceability, this is the perfect backup system for your irreplaceable data. WD's My Book Mirror Edition dual-drive storage system automatically mirrors your valuable data for extra protection. The USB 2.0 interface and a powerful combination of features make this system the storage solution of choice for photographers, home users, small offices, and anyone looking for extra assurance that their data is safe. Available in 2TB and 1 TB.