2013/7/30 Rick James <rjames@stripped>
> Elevator... If the RAID _controller_ does the Elevator stuff, any OS
> optimizations are wasted.
> And there have been benchmarks backing that up. (Sorry, don't have any
> links handy.)
> RAID 5/10 ... The testing I have done shows very little difference.
> However, you can slant the conclusion by picking one versus the other of:
> "For a given amount of disk space... RAID-X is better than Y."
> "For a given number of drives... RAID-Y is better than X."
The tests I have done with RAID5 vs RAID10 the difference is huge, at least
in our clusters with heavy writes.
We usually do RAIDS over 4 or 8 SAS disks (15krpm).
The performance of each type of RAID needs to be tested for your concrete
scenario, you can find lot of benchmarks out there, but you need to test
your workload to be sure what works better for you. As Rick said, with
BBUs, disk schedulers, write back/write thru configuration etc things can
The last tests with SSD disks shows no difference, so for the new servers
with SSD we're going for RAID5 as you get more disk space :-)
Just my 2 cents!