How to set concurrency parameters?

[Yuzhang Han]

Hi,

I know these parameters can be set to tune the number of parallel scans 
on each region:

targetConcurrency, maxConcurrency, threadPoolSize, queueSize and 
maxIntraRegionParallelizaioin.

But I am wondering if there are some rules of thumb for setting their 
values optimally? Perhaps my cluster configuration is useful for you:

3 region servers, 8 cores and 8GB RAM on each. My table has 6 regions, 2 
regions/region server, 5 million rows.

Thanks!