Persistent connection among nodes to communicate and redirect request

[Niteesh kumar]

while looking at netstat table i observed that my cluster nodes not 
using persistent connection  to talk among themselves on port 9160 to 
redirect request. I also observed that local write latency is around 
30-40 microsecond, while its takes around .5 miliseconds if the chosen 
node is not the node responsible for the key for 50K QPS. I think this 
attributes to connection making time among servers as my servers are on 
same rack.

how can i configure my servers to use persistent connection on port 9160 
thus exclude connection making time for each request that is redirected...