Thank you so far for your answer.
I don´t think that the RAID-Levels are the reason for that poor performance.
IIRC RAID10 has good (the best?) performance regarding reading (almost all discs if controller can manage it) and writing (50% of used discs).
RAID6 has more workload because of the parity on the discs, but let´s be honest... A RAID6 volume with 11 disks should be able to get 300MB/s reading or writing nor? (my RAID5 Volume in my homelab gets 250MB/s / 200MB/s reading / writing with 4 disks!)
Why do you think, the switches are not powerful enough?
190 MPPS with both switches @MTU1500 would means there is (theoratically) a performance of over 30 MPPS ...
30 million pakets per second are not enough? 
Correct me, if i am wrong ...
Thanks in advance...
Ralph