Home > Storage > PowerVault > Guides > Dell PowerVault ME5 Series: VMware vSphere Best Practices > ESXi iSCSI setting: delayed ACK
Delayed ACK is a TCP/IP method of allowing segment acknowledgments to transport upon each other or on other data that is passed over a connection. The goal of this method is to reduce I/O overhead. One side effect of delayed ACK is that if the pipeline is not filled, acknowledgment of the data is delayed. This effect manifests as higher latency during lower I/O periods. Latency is measured from the time data is sent to when the acknowledgment is received. With disk I/O, any increase in latency can result in decreased performance. If higher latency during lower I/O periods is observed in the environment, disabling delayed ACK may resolve the issue. Otherwise, consult Dell Support.
VMware KB article 1002598 provides more information, including instructions for disabling delayed ACK on ESXi.