How to choose the right RAID level

Posted on February 27th, 2009.

RAID Recovery - How to choose the right RAID level

Different RAID levels are for different kinds of requirements; it could be for organization, business or personal use. For example, for high performance reads and writes, it is better to avoid RAID 6 and use some smaller disk drives; on the other hand, to store mass amount of data where rebuild is possible RAID 5 and 6 is recommended to be the best option to application needs.

The following issues should be kept in mind before deciding which RAID will be the right choice:

One should avoid using disk drives that have higher chances of failure, so selecting RAID level 1 would be solution to avoid the performance impact as it has capacity to store data across multiple disks simultaneously.
Queries like for a RAID controller how many rebuild can happen concurrently, does a subsequent rebuild, after the replacement of failed drive, need to occur to relocate the additional disk in its original location should be considered; otherwise one is quite likely to become the victim of the problem like frequent drive failure which negatively affect the overall performance.
What RAID levels are supported, what is the granularity of RAID levels to function simultaneously and over what number and kinds of disk drive all are important information to know. Also check what flexibility you are provided with for tuning RAID as well as automatic RAID tuning by the storage system or controller for hands off operation.
Recognize how RAID implementation is optimised for sequential input/output application compared to random I/O over reads as well as writes. For database updates and processing, one needs his system to be optimised small random I/Os, but for larger sequential video or audio files one requires RAID system independent to support large sequential I/O operation. For larger IOPs, then look for IOPs per second to go down while MB/sec goes up.
User should have knowledge about what should be done to alleviate performance impact on both write and read level and during rebuilding process for duel based RAID implementation.
Keeping requirement of various applications in mind, one needs to know what level of service is needed and why to use RAID to meet up daily challenges or odds. Users should also know the right RAID level to support sequential or random small or large I/O processing, reads compared to writes.
If a RAID offload or accelerator engine is used, one has to estimate what output is expected, and after using, what performance was actually achieved.
A common misconception is that more cache is always a better option and also that higher cache utilization means improved performance. The ground reality is, only a few systems need more cache to offset in order to move data quickly to or from hard disk. It is always advisable to go for a cache of high performance and make sure it is utilized effectively.