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VMWARE WHITE PAPER

3.3. Netperf Throughput

Netperfisamicro-benchmarkthatmeasuresthethroughputofsendingandreceivingnetworkpackets.Inthisexperimentnetperf

was congured so packets could be sent continuously without having to wait for acknowledgements. Since all the receive trac

needs to be recorded and then transmitted to the secondary, netperf Rx represents a workload with signicant FT logging trac.

As shown inFigure 6, with FT enabled, the virtual machine received 890 Mbits/sec of trac while generating and sending 950 Mbits/

sec of logging trac to the secondary. Transmit trac, on the other hand, produced relatively little FT logging trac, mostly from

acknowledgement responses and transmit completion interrupt events.

Figure 6. Netperf Throughput

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FT Disabled

FT Enabled

Netperf throughput

Mbits/sec

Receives Transmits

FT trac Rx: 950 Mbits/sec

FT trac Tx: 54 Mbits/sec

3.4. Netperf Latency Bound Case

In this experiment, netperf was congured to use the same message and socket size so that outstanding messages could only be

sent one at a time. Under this setup, the TCP/IP stack of the sender has to wait for an acknowledgment response from the receiver

before sending the next message and, thereby, any increase in latency results in a corresponding drop in network throughput.

Noteinrealityalmostallapplicationssendmultiplemessageswithoutwaitingforacknowledgement,soapplicationthroughputis

not impacted by any increase in network latency. However since this experiment was purposefully designed to test the worst-case

scenario, the throughput was made dependent on the network latency. There are not any known real world applications that would

exhibit this behavior. As discussed in section 1.4, when FT is enabled, the primary virtual machine delays the network transmit until

the secondary acknowledges that it has received all the events preceding the transmission of that packet. As expected, FT enabled

virtual machines had higher latencies which caused a corresponding drop in throughput.