It's indeed very perplexing why the parity check CPU % is so much higher with v6.    I'd have actually expected it to be lower, since the 64-bit architecture should be more efficient ... but I had a 31% increase in my parity check time when I moved my media server from v5 to v6.1.3.    [Managed to trim that to a bit over 6% by disabling display updates and changing the disk tunables -- but it still have a VERY high CPU utllization ... very close to 100% for a good bit of the check.]

 

I did parity check on 3tb its said 5 days went to work and came back was done  17 hours