If the network or cluster performance does not seem optimal, it is easy to check for pause frames on a PowerScale cluster.

If pause frames are reported, discuss these findings with the network engineering team before making any changes. As mentioned, changes must be implemented across the network, ensuring all devices recognize a pause frame. Contact the switch manufacturer’s support teams or account representative for specific steps and caveats for implementing flow control before proceeding.

4th and 5th generation Isilon nodes

On a 4th or 5th generation Isilon cluster, check for pause frames received by running the following command from the shell:

isi_for_array -a <cluster name> sysctl dev | grep pause

Check for any values greater than zero. In the example in the following figure, the cluster has not received any pause frames. If values greater than zero are printed consistently, consider flow control.

Figure 5.   Checking for pause frames

6th generation Isilon nodes

For 6th generation Isilon nodes with ix NICs, check for pause frames with the following commands:

infPerf-1# sysctl -d dev.ix.0.mac_stats.xon_txd dev.ix.0.mac_stats.xon_txd: Link XON Transmitted <<<Pause frame sent infPerf-1# sysctl -d dev.ix.0.mac_stats.xon_recvd dev.ix.0.mac_stats.xon_recvd: Link XON Received <<<Pause frame received infPerf-1# sysctl -d dev.ix.0.mac_stats.xoff_txd dev.ix.0.mac_stats.xoff_txd: Link XOFF Transmitted <<<Resume frame sent infPerf-1# sysctl -d dev.ix.0.mac_stats.xoff_recvd dev.ix.0.mac_stats.xoff_recvd: Link XOFF Received <<<Resume frame received