LaCie 2BIG NAS User Manual page 266

RAID 1
RAID 1 provides enhanced data security since all data is written to each disk in the volume. If a single disk fails,
data remains available on the other disk in the volume. However, due to the time it takes to write data multiple
times, performance is reduced. Additionally, RAID 1 will cut disk capacity by 50% or more since each bit of data
is stored on all disks in the volume.
Note on RAID 1 disk requirements: A standard RAID 1 configuration includes two disks of equal capacity.
However, NAS OS allows you to create a RAID 1 volume with up to three disks or, three disks plus a spare. It
is also possible to create a RAID 1 volume using a single disk. While such a volume cannot provide any data
protection, it is ready for expansion when you add a new disk. Data protection would become available once
the second disk is added to the RAID 1 volume.
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