How to select the best RAID Level configuration

Selecting the Best RAID Level Configuration

Selecting an appropriate RAID level used to be a simple matter, but with time newer options are available and thus it becomes more difficult to select the most appropriate option. Several factors like the need for redundancy, budget, performance of read and write operations, availability of built-in hot spare and number of drives impact the final decision anyone makes. Below is a table that should help individuals better select the RAID level that is most adequate for the logical drives available on the storage space. Using your requirements for performance and reliability you can make a more educated decision on which level to chose.

 

RAID Level	Redundancy	Disk Drive Usage	Read Performance	Write Performance	Built-in Hot-Spare	Minimum Disk Drives
RAID 0	No	100%	www	www	No	2
RAID 1	Yes	50%	ww	ww	No	2
RAID 1E	Yes	50%	ww	ww	No	3
RAID 10	Yes	50%	ww	ww	No	4
RAID 5	Yes	67 – 94%	www	w	No	3
RAID 5EE	Yes	50 – 88%	www	w	Yes	4
RAID 50	Yes	67 – 94%	www	w	No	6
RAID 6	Yes	50 – 88%	ww	w	No	4
RAID 60	Yes	50 – 88%	ww	w	No	8

In general the more hard drives you have available in the array the better the performance. However, one must be careful nowadays as with increased storage space comes higher risks. Hard drives are rated and provide a number of errors per number of reads. Obviously the more space available the more likely a read/write error is to happen. Now, the more drives you have the higher that probability of an error occurring across the array. For that reason I recommend having a professional RAID controller that is able to address this issue. I´ve used cheap integrated ones before and whenever they come across a minor error the entire array becomes un-operational and lost.

Another important aspect to keep in mind is that certain RAID levels as RAID 5 and 6 use distributed parity, which means that the controller has to be constantly computing the parity information and that introduces a performance hit and utilization of the controller. Raid 1 or 10 in contrast have not such parity operations.

I hope this information helps and let me know which is your favorite RAID level! I’m personally using RAID 1E vs RAID 5 and 6 for performance reasons.