This article discusses reducing Fault Tolerance (FT) logging traffic for disk-read intensive workloads.
When FT is enabled, all the inputs to the virtual machine are recorded and sent to the secondary host over the vmkernel port which has been designated for Fault Tolerance logging.
The inputs to the virtual machine include incoming network traffic as well as disk reads. If the virtual machine is doing throughput-intensive disk reads (such as sequential I/O), a lot of logging traffic needs to be sent to the secondary host
For example, a virtual machine doing disk reads at a 80MB/sec generates at least 80 x 8 = 640Mb/sec of logging traffic.