On 22.02.2015 22:53, NeilBrown wrote:

There is no "Optimal" without reference to a particular work load.  Or
particular hardware.

Do you know of such a reference? I mean, some stats that show type of 
workload / chunk size. The only one I've found is the 5 year old 
benchmark that was done ( 
http://louwrentius.com/linux-raid-level-and-chunk-size-the-benchmarks.html) 
- which shows that under benchmarking with dd that 64 is preferred.

-- 
chs