ESXi 6.5 includes a new native driver (vmw_ahci) for SATA AHCI controllers, but that introduces performance problems with a lot of controllers and/or disks.

Try to disable the native driver and revert to the older sata-ahci driver by running

 esxcli system module set --enabled=false --module=vmw_ahci

Reboot the server after changing it and your performance should be OK again.

To get a list of mounted storage execute the following command on the cli of an ESX5.x host:

esxcli storage filesystem list

In ESXi 5.1 you could use the command ethtool -i vmnicX to get the firmware and driver version for the Network interface card. In 5.5 you get an error: Can not get control fd: No such file or directory.

 

To get the firmware and driver version use the following command in 5.5:

esxcli network nic get -n vmnicX

To get a list of nics:

esxcli network nic list

On a Cisco Nexus 1000v port-group you can enable promiscious mode on a port-group:

no mac auto-static-learn

This can come in handy for Loadballancing purposes.