Double-parity RAID, commonly known as RAID 6, safeguards against data loss by allowing up to two consecutive drive failures

What is RAID 6?

RAID 6 eliminates the risk of data loss if a second hard disk drive fails or an unrecoverable read error occurs while the RAID array is rebuilding. In a RAID 6 enabled system, a second set of parity is calculated, written, and distributed across all the drives. RAID 6 is obviously more secure than RAID 5, but do you pay a performance penalty for this added security?

RAID 5 vs. RAID 6 Performance

Because RAID 6 requires a second set of parity calculations, this additional step slows the write performance. Performance benchmarks show that a typical RAID controllers can suffer more than a 30% drop in overall write performance in RAID 6 when compared to a RAID 5. However, RAID 5 and RAID 6 read performance remain unaffected. AMCC/3Ware has implemented sophisticated advanced stripe handling technology that maximize RAID 6 performance by dramatically minimizing the write performance penalty. Simultaneous parity calculations and dedicated silicon-based stripe handlers radically reduce the write penalty on 3ware controllers to less than 10% between RAID 6 and RAID 5.

Summary

RAID 6 represents an incredible change in the RAID landscape. It provides customers with higher levels of data protection, data availability and fault tolerance than RAID 5. By assuring data availability following a second drive failure, users can rest assured that they are enjoying maximum data protection, both in normal and degraded modes. And, with RAID 6 enabled AMCC/3ware controllers, RAID 6 will not cripple performance. However, it is important to remember that RAID 6 does not come without costs. RAID 6 requires the equivalent capacity of two drives in the array to be dedicated to storing only parity information. Also, most RAID 6 systems carry a write performance penalty due to the additional parity calculation. AMCC/3Ware simultaneous parity calculations mitigate these performance impediments to provide the fastest RAID 6 solution available.

This innovative technology is available from Pogo Linux today in several product configurations.