Verbatim Pro RAID Guide De L'utilisateur page 11

Available capacity is the combined capacity of both drives.
If either disk fails in RAID 0 then the LED of the failed drive will change to RED.
RAID 1 (also called Mirroring) stores a duplicate set of data onto both disks, so that if one
disk fails all data can be recovered from the other disk. Available capacity is equal to that
of only one of the two included drives.
If either disk fails in RAID 1, then the LED corresponding to the failed disk will change to
RED. The remaining operational disk can continue to be used until the failed disk has been
replaced. However, in this instance there is no longer any data protection provided by the
second, failed drive.
If you have been using RAID 1 mode and there is a subsequent failure of either of the two
drives, you can disassemble the enclosure and replace the failed drive with a new drive.
After reassembling the enclosure, leave it disconnected from your computer and power
it up. When the new drive is detected during the power-on sequence, the full data of the
original drive will be rebuilt onto the new drive. This rebuilding procedure can take many
hours (more than 5!) to complete. During the rebuilding procedure, the LED of the original
good drive will flash BLUE, while the LED of the new replacement drive will flash RED.
After the array has rebuilt successfully both LEDs will change to BLUE.
Concatenation (RAID Mode Switch Setting = "BIG") combines both physical disk drives
into a single virtual disk. Available capacity is the combined capacity of both drives.
This mode provides no data redundancy. If either disk fails in Concatenation mode, then
the array will no longer mount to your computer.
If either disk fails in Concatenation mode, then the LED corresponding to the failed disk
will change to RED.
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