RAID (Redundant Arrays of Independent Disks) has its own place in the storage arena, especially with storage
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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.
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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. Explains Niket Trivedi, Storage
Engineer, Visa International, Singapore, "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. According to Aman Munglani, Principal Analyst, Gartner India, "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. Says Pritam Pawar, Storage Consultant, Network Techlab, "Nowadays we get intelligent
raid controllers which enhance the performance. SSD
drives from different vendors provide high IOPS, which reduce theperformance
impact for RAID 6."
Should you opt for it?
Although security of data is a top priority for most organizations, it is not necessary to jump on
the RAID 6 bandwagon. Organizations should move from RAID 5 to RAID 6 only if they feel that their
business uptime is more critical. Remarks Trivedi, "Personally, I would stick to RAID 5 rather than
go in for RAID 6 because the former will always perform better and faster. But any particular
application needing uptime with low disk performance should be sitting in a RAID 6 configuration.
Please note that RAID 5 is faster than RAID 6."
The main pre-requisite to be a RAID 6 organization is the existence of data that requires high
availability and high
protection.
There are certain recommended configurations for RAID 6 that one can go for. According to Pawar,
"The number of disks one should use for a raid array should be a minimum of four drives. Second,
the stripe size setting should be according to the data requirement (OLTP/database)."
Trivedi adds, "It depends on the expected performance versus how much risk we are allowed to take."
Hardware suppliers of storage should perform a test for individual customers with their performance
requirements and configure accordingly.
The Indian scene
Is India on a RAID 6 ride or will it always go side-by-side with other RAID levels? According to
Srinivas Rao, Director, Presales & Solutions, Hitachi Data Systems, "A lot of customers are
going for RAID 6 because the density of disk drives has gone up, and the chances of losing data in
case of a disk failure in the RAID 5 configuration are more. RAID 6 is mostly deployed on Serial
ATA because the density there is more."
Storage vendors are now offering the RAID 6 feature in their storage boxes; this might pick up
aggressively since virtualization
and cloud
computing are fast catching up among Indian organizations.
Comments Munglani, "A lot of Indian organizations are already adopting RAID 6. Extremely tech-savvy
companies are more on the RAID 6 vine. However, even organizations with Fibre Channel drives with
mission-critical applications have started implementing it."
Thus, it's not a question of competition between RAID 5 and RAID 6. One can always put
mission-critical data on RAID 6 and let the rest of it reside on the former. There will be no real
need to shift completely from RAID 5 to RAID 6. With data security becoming vital even for SMBs,
RAID 6 will slowly go hand in hand with its forerunner.