We have a Dell PowerVault MD3200i connected to a server via iSCSI using 2 Dell switches (PowerConnect 6224) at 1GB. The server has VMware ESXi 6.5 installed and it's connected to the PowerVault using 2x 1GB NICs connected to each switch.
I have a VM created and one virtual disk assigned to the virtual machine that reside on the PowerVault. I have enable Jumbo Frames on each switch, on VMware and on each interface on the PowerVault, but I didn't notice any increment on the performance.
I was testing the performance on the virtual disk using IOmeter, and without Jumbo Frames enable I get around 739 Total IOPs and 28.5 Total Mbs per seconds. With Jumbo Frames enabled, I get about 640 Total IOPs and about 22-24 Total Mbs per seconds.
Shouldn't be the other way around? I thought I would get a better performance setting MTU to 9000, but it seems to be the opposite.
I confirm that Jumbo Frames are enabled on all the device in the connections (VMware server, switches and PowerVault) because I can "ping" from VMware to the PowerVault using vmkping -d -s 8972 *ip-powervault* and I receive reply from the PowerVault without errors.
Am I missing something? or is this something with the PowerVault MD3200i?
Thanks and best regards.
Best Answer
Enabling jumbo frames for iSCSI connections usually boosts the performance on larger packets/blocks so you have to ensure that you are running your benchmarks using 64K (for example) block size for testing.
Do not expect to get more than 5%-15% performance boost with jumbo frames.