RAID 6: A comparison with RAID 5

RAID (Redundant Arrays of Independent Disks) has its own place in the storage arena, especially with storage as a concept taking off quite seriously in India. There are half a dozen RAID levels which organizations can choose from; the more persistent one seems to be RAID 5. With criticality and protection of data becoming more vital with each passing day, RAID 6 is slowly making its way into the storage infrastructure of Indian organizations.


The pros and cons
The main question that arises: Why should organizations shift to RAID 6 leaving their comfort zone of a certain RAID level? Also, for which organizations does it make sense? To find the answer, one needs to take a close look at the advantages of RAID 6 as well as its downside.

The biggest advantage is its ability for dual disk parity. Currently, some hard disk drives (HDDs) have a capacity of almost 1 TB, in contrast to HDD capacities just a decade ago which were not over 30 GB. Thus, the amount of time needed to fix the fail drive would be more, and it would be a smarter decision to have dual disk failure protection. RAID 5 seems to work really fine with SMBs, which are cost-conscious and do not have any great need to extra protect their data, though in certain environments it may be otherwise.

Apart from the additional protection, RAID 6 provides high fault tolerance, thus sustaining simultaneous disk failures. It is a safer option given that in today's environment there are a lot of organizations having SATA-based drives which are extremely huge in terms of capacity but low on reliability. Thus, RAID 6 is more valid when there is a large capacity to address. SATA is less reliable than SCSI drives or FC drives, hence when environments need added security, RAID 6 makes a lot of sense.

On the downside, one would need to buy a lot more in terms of raw disk space. It will cost more upfront due to the additional drive that needs to be procured. As two of the disk drives are being used for parity, the dilemma is between raw disk space and usable space.

Also, for RAID 6, one needs a more complex system with a method for encoding. One also needs hardware acceleration, otherwise the performance suffers. Thus, performance loss is one more disadvantage. Nowadays we get intelligent raid controllers which enhance the performance. SSD drives from different vendors provide high IOPS, which reduce the performance impact for RAID 6.