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Storage and Availability Management

Low Latency Transport Suggestions

Created: 10 Sep 2009 • Updated: 11 Jun 2014
Sandeep Agarwal's picture
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If you want to reduce extra traffic on the LLT links one small thing to do would be to add the following line to /etc/llttab on all the nodes in your cluster (say 2 node cluster):
exclude 2-31

What the above line does is that it assumes that your cluster will always have only 2 nodes (0 and 1) and hence extra packets will not be sent to discover the other nodes periodically. One caveat is that you won't be able to add a node to your cluster on the fly. You could also change the above line to be:
exclude 8-31
and in that case you can grow your 2 node cluster to a maximum of 8 nodes on the fly.

One more thing to note when using LLT is to never have spanning-tree enabled on the switch ports which are used to connect the LLT links. Spanning tree causes a delay in sending pkts when the port is enabled and this can cause the cluster nodes to not join properly.