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NetApp Knowledge Base

How to increase the TCP receive window buffer size for Inter-Cluster and IntraCluster Volume SnapMirror

Last Updated:

Applies to

  • ONTAP 9
  • Clustered Data ONTAP 8


Inter-Cluster and IntraCluster SnapMirror uses the network service named ctlopcp

  • The ctlopcp service has a tunable TCP receive buffer window for Inter-Cluster and IntraCluster connections.
    • The Inter-Cluster TCP receive buffer window defaults to 2 MB, the IntraCluster TCP receive buffer window defaults to 256 KB.
    • The TCP receive buffer windows can be increased up to 7 MB, and can be decreased to 256 KB.
  • Increasing the Inter-Cluster TCP receive buffer window can increase the effective throughput when working with high-capacity WAN connections.
    • However, this may not be necessary due to the increased number of active TCP streams used for replication.
    • For more information, see Section 2.4 "Network Connections for Inter-Cluster SnapMirror" in TR-4015.
  • Inter-Cluster TCP receives buffer windows auto-tune by default.
    • These start at 64KB per TCP stream and grow to a maximum of the configured value (default 2MB) to accommodate InterCluster replications.
    • Once grown, the receive buffer window does not shrink as long as the TCP stream remains open.



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