On an LLT over RDMA network, the default RDMA receive-buffer size is 64K and the number of receive-buffers that can be allocated is 1000.
To tune the LLT variables for RDMA links
LLT_MAXADVBUFS=4000
When you increase the number of receive-buffers to a maximum value of 4000 the IO performance improves, provided the cluster nodes have sufficient memory.
Append the /etc/sysconfig/llt file with the following value.
LLT_ADVBUF_SIZE=8192
set-flow highwater:10000 set-flow lowwater:8000 set-flow window:5000 set-flow rporthighwater:10000 set-flow rportlowwater:8000