Running large and high demanding hypervisor connected to SAN storage require jumbo (large MTU) frames to enhance I/O performance to the guests virtual machines.
To achieve that, you need to use the command line since vSphere console do not allow to do such thing.
1. Stop all guest virtual machine and put the hypervisor in maintenance mode.
[ Using the shell, use the following commands ]
2. Configure de virtual switch to accept jumbo frames :
/usr/sbin/esxcfg-vswitch -m 9000 vSwitch1
3. Remove the VMkernel network card from Port Group (replace 0.0.0.0 with proper IP address) :
/usr/sbin/esxcfg-vmknic -d -i 0.0.0.0 VMkernel
4. Add back the VMkernel network card (with jumbo frames) to Port Group
/usr/sbin/esxcfg-vmknic -a -i 0.0.0.0 -n 255.255.255.0 -m 9000 VMkernel