http://www.dvestore.com/brands/LaCie.html Here we see the LaCie 2Big Quadra performing in RAID 1 and 0 "Mixed" mode. A great combination of speed and mirroring with an acceptable loss in capacity. In this instance we're using a 3TB model - that's Two 1.5TB disks inside the enclosure. After switching to "Mixed Mode" on the back we're able to get 1.5TB of "Fast" storage and a 750GB Partition of "Safe" storage. The Safe storage is mirrored on both drives, in case one fails, you have a total back up. The fast partition would be lost, so knowing this, you can use the Fast drive for working files, and the Safe drive for backup.Need one today? Give us a call at 1-877-353-8077 or stop by http://www.dvcreators.net/lacie-2big-quadra/From the manual:In Mixed mode, the two physical disks are combined so that twological volumes mount simultaneously on the desktop:✦✦ One Safe volume (RAID 1) where data is automatically mirroredon each physical disk. This volume uses 50% of theavailable capacity of each disk (the available capacity cannotexceed 50% of the lowest-capacity single disk).Important info: If one physical disk fails, the data of theSAFE volume is available on the second disk. Only 25% of fullcapacity is protected by mirroring. In this case, data on the Fast(RAID 0) volume will be lost.✦✦ One Fast volume (RAID 0) enables the user to work with thehigh speed of RAID 0.