LaCie 2BIG NAS User Manual page 207

RAID 1
RAID 1 is a secure RAID mode that is available if the LaCie 5big NAS Pro has only two disks installed. RAID 1
provides data safety since all data is written to each disk at the same time. In the event of a single disk failure,
data remains available on the other disk. Due to the time it takes to write the data twice, performance is slightly
reduced. RAID 1 is a good choice when safety is more important than speed. However, RAID 1 also reduces the
available disk space by 50% due to the need to write each bit of data on each hard drive.
RAID 5
In RAID 5, data is striped across all disks (minimum of three) and a parity block for each data block (P in the
illustration below) is written on the same stripe. If one physical disk fails, the data from the failed disk can be
rebuilt onto a replacement disk. No data is lost in the case of a single disk failure, but if a second disk fails
before data can be rebuilt to a replacement hard drive, all data in the array will be lost.
RAID 6
In RAID 6, data is striped across all disks (minimum of four) and two parity blocks for each data block (p and q in
the illustration below) are written on the same stripe. If one physical disk fails, the data from the failed disk can
be rebuilt onto a replacement disk. This RAID mode can support up to two disk failures with no data loss. RAID 6
provides for faster rebuilding of data from a failed disk.
LaCie 2big NAS | LaCie 5big NAS Pro User Manual 207