Large file copy to NFS mounted directory causes delay in other application packets

From: Manavalan Krishnan
Date: Wed Nov 09 2011 - 00:28:24 EST


Hi All

I have two systems with two network interfaces each(eth0 and eth1). I am running linux-HA (heartbeat deamon) on both the systems and they use eth0 for exchanging heartbeats. I have NFS mounted directory in one system and the NFS client uses the interface eth1.

I try to copy a large file to NFS mounted directory. But the heartbeat daemons misses the heartbeat packets from peers while copy is under progress. I did tcpdump and found that the heartbeat packets are delayed for few seconds before sent out on eth0. When I stop the file copy, the heartbeats are delivered properly. It seems linux kernel somehow giving priority for NFS packets(generated from the file copy) over other application packets.

Any thoughts on this behavior? Is there any way we can avoid this so that application packets get equal chance while large file copy to NFS mounted directory under progress?

Thanks Much
Mana

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