What is RAID 6?

RAID 6 is the latest and newest RAID level that safeguards against data loss even if two hard drives fail at once. RAID 6 stripes blocks of data across an array of drives, but it calculates two sets parity information for every block. The goal is to have a safer data array that can withstand multiple consecutive failures. Performance-wise, RAID 6 is generally slightly worse than RAID 5 in terms of writes due to the added overhead of more parity calculations, but may be slightly faster in random reads due to spreading of data over one more disk.

RAID 5 vs. RAID 6 Performance

Write performance on a RAID 6 array is reduced in comparison to RAID 5, because of the second set of parity calculations required for RAID 6. 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 the read performance of a RAID 6 array is comparable to a RAID 5 array.

Is it worth it?

The downsides to RAID 6 is an more expensive RAID controller and a more inefficiency drive setup, but the end result is more secure data that can two consecutive drive failures. However with advances in RAID controller technology, most controllers have a hot-spare option. If hot-spare is enabled, the controller will replace a hard drive in the event of a disk failure, with an attached drive in standby mode. Multiple hot-spares can be assigned to help restore your degraded array, in case of multiple failures.

For the most mission critical applications, users should practice the use of a RAID 6 array, with added hot-spares for quick replacements of failed drives.