When building any RAID array you need to consider how many IOPs you require, and what impact different RAID levels have on the number of IOPs. For example if you have 2 drives in RAID 1, for each single IOP you write to the (front-end) RAID 1 array, you need to do 2 IOPs (back-end – one to each drive). Using RAID 5 or 6 can have significant impact on performance, and the number of front-end IOPs to back-end IOPs needs to be taken into consideration.

This is a regular problem we come across while building storage servers, depending on the speed of the drives, the number of drives, storage requirements, and required IOPs for the application we need to make an appropriate RAID level decision.

Back-end Write IOPs Required for every Front End Write:
RAID 0 – 1 IOP
RAID 1 – 2 IOPs
RAID 5 – 4 IOPs
RAID 6 – 6 IOPs
RAID 10 – 2 IOPs

As an example, a RAID 6 array with 6 drives would perform the same number of IOPs a single drive while writing.