We manage a mid-sized array of images (4kb -> 1mb or so) using DAS hardware that is NFS exported to various webservers. We have traditionally used raid5 for the safety-net and storage-gains, rather than losing capacity for the sake of better speeds with raid10. We have reached a point where our 16TB arrays are suffering, and read times are slowing down and becoming noticeable to the end user.
I am considering purchasing a new array to test with various raid10 configurations, but before I can get approval for that, I will need to be able to spec the approximate capacity for the new system which leads me to my ultimate question:
How is disk performance affected by spanning N-number of drives? I know that write/read perf is different, so for the sake of this conversation we will limit it to reads.
eg, Would 4 drives in a raid-10 outperform 6 drives in a raid-10, etc.
Is there a metric for establishing this, or known constraints to consider? I know that there is no silver-bullet that works everywhere, but I am hoping for some best practices thoughts.
Thanks for helping me to wrap my head around this one!