Lacie 4big Quadra White Paper - Page 4

LaCie RAID Technology White Paper RAID 3 RAID 3 uses byte-level striping with a dedicated parity disk (Disk 4 in the illustrations, right) so that one volume mounts on the computer. A RAID 3 array can tolerate a single disk failure without data loss. If one physical disk fails, the data from the failed disk can be rebuilt onto a replacement disk. If a second disk fails before data can be rebuilt to a replacement drive, all data in the array will be lost. Applications RAID 3 provides good data safety for environments where long, sequential files are being read, such as video files. Disk failure does not result in a service interruption because data is read from parity blocks. RAID 3 is useful for people who need performance and constant access to their data, like video editors. RAID 3 is not recommended for intensive use with nonsequential files because random read performance is hampered by the dedicated parity disk. LaCie Products with RAID 3 ✦✦ LaCie 4big quadra RAID 3 A1 A4 B1 B4 C1 C4 Disk 1 A2 A5 B2 B5 C2 C5 Disk 2 A3 A6 B3 B6 C3 C6 Disk 3 Ap(1-3) Ap(4-6) Bp(1-3) Bp(4-6) Cp(1-3) Cp(4-6) Disk 4 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 3 Capacity Is Calculated Each disk in a RAID 3 system should have the same capacity. Storage capacity in a RAID level 3 configuration is calculated by subtracting the number of drives by one and multiplying by the disk capacity, or C = (n-1)*d where: C = available capacity n = number of disks d = disk capacity For example, in a RAID 3 array with four drives each with a capacity of 1000GB, the total capacity of the array would be 3000GB: C = (4-1)*1000 Page 4