Lacie 4big Quadra White Paper - Page 8

LaCie RAID Technology White Paper RAID 6 In RAID 6, data is striped across all disks (minimum of four) and a two parity blocks for each data block (p and q in the diagram at right) is 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. Applications RAID 6 provides data reliability with the addition of efficient rebuilding in the case of a failed drive. RAID 6 is therefore useful for people who need serious security with less of an emphasis on performance. LaCie Products with RAID 6 ✦✦ LaCie 5big network RAID 6 A1 B1 C1 Dp Disk 1 A2 B2 Cp Dq Disk 2 A3 Bp Cq D2 Disk 3 Ap Bq C3 D3 Disk 4 Aq B3 C3 D3 Disk 5 RAID 0 RAID 1 RAID 3 RAID 3+Spare RAID 5 RAID 5+Spare RAID 6 RAID 0+1 RAID 10 Concatenation JBOD RAID Selection How RAID 6 Capacity Is Calculated Each disk in a RAID 6 system should have the same capacity. Storage capacity in a RAID 6 configuration is calculated by subtracting the number of drives by two and multiplying by the disk capacity, or C = (n-2)*d where: C = available capacity n = number of disks d = disk capacity For example, in a RAID 6 array with five drives each with a capacity of 1000GB, the total capacity of the array would be 3000GB: C = (5-2)*1000 Page 8