Scale IO cluster loading balance issue ?

Hi all

I attempted to add a new node (192.168.38.35) into ScaleIO cluster.I observe that asymmetric loading at new node.

Node1 IOPS (192.168.38.34): 35000

Node2 IOPS (192.168.38.35):   9000

Node3 IOPS (192.168.38.36): 25000

Node4 IOPS (192.168.38.37): 30000

The appearance which asymmetric IOPS spacial on new node,why the new node 192.168.38.35 not completely share cluster loading ?

Maybe any suggestion for rebalance mechanism can explain it ?

About linear scaling feature, I got only 10% - 15% growth when add a new node in my lab.(all nodes spec are same)

Is the growth value reasonable ?

Thanks.