ESXi NFS Read Performance: TCP Interaction between Slow Start and Delayed Acknowledgement

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May 11, 2020

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In this paper, we explain how a very minor packet loss rate (as low as 0.02%) on the network could trigger an undesirable interaction between TCP slow start on a sender and delayed acknowledgement on the receiver, leading to unexpectedly poor data transfer throughput. We then describe a scenario in which this interaction manifests itself in the context of ESXi read operations from an NFS server. A workaround is available in ESXi 7.0.