Here we see a two drive solution pushing over 200MB/sec on a "Fast" Partition in RAID 0 and a "Safe" Partition pushing 100MB/sec in RAID 1. This is called RAID 1 and 0 Mixed Mode achieved with just two drives in one enclosure. Previously you had to choose one or the other, fast or safe, now you can have both in one chassis at an affordable price. Note, you still do lose 25% of the capacity in RAID 1 and 0. Most content creators will find 25% an acceptable trade off for the peace of mind backup.

Example two 1.5TB drives (3TB total)

These two partitions you see in the video on the desktop as two mounted drives:

Fast Partition 1.5TB
Safe Partition 750GB

Total = 2.25TB out of a 3TB drive.

In the event of single drive failure, all of the data on the Fast Partition will be lost. The Safe drive will still have all of it's data.

For my "Aperture Library" with all of my photos, I work from the "Fast" drive you see mounted on the Desktop and use Apple's Time Machine to automatically back up the library to the "Safe" drive. Keep in mind that you can only have 750GB backed up (mirrored) on a 3TB drive - not enough to backup the entire Fast volume. Example, I do not back up my Final Cut Pro "Render" files, only my "Capture Scratch" and working files.
dvcreators.net/lacie-2big-quadra/
See PDF manual lacie.com/download/manual/2big_Quadra_en.pdf