"As for any testing, I think we'd find the problem with trying to
objectively measure a set of configurations is the lack of good
"general" workload, as there's no such thing."
In the past I have invested quite a bit of time trying to find RAID calculators and perform accurate benchmarks -- but I have to agree with Mark on this one, in the end the experiments generally just end up telling you how well the particular experiment performs on your particular hardware.
Some of the complexities:
- Read / Write percentages
- Sequential vs Random patterns
- Block sizes of data written
- The effect of caching
- Controller bottlenecks
- The specifics of how the controller implements the RAID
- Total number of drives
- Filesystem block sizes, or in the case of Linux or SANs which filesystem
And these are just what I can think of off the top of my head.
Perhaps more useful would be a series of blog posts about how to properly profile and simulate a real world workload. For that you just need to find a DBA with a company or client that will let them be open about this particular project.
You also might scale back what you are doing and do something like try to figure out how well RAID 10 scales as you increase the size of the array. That might be intersting even if you are just doing a small set of workloads.
In the end I don't think you can draw a conclusion about what is the best choice. Putting logs on their own array is also a safety concern. Also, in general logs are sequential so this helps simplify troubleshooting IO issues. Both of these often will outweigh performance implications for many people.