If you need to use jumbo frames on your ISCSI you need to run this command from the command line of the ESX host:
esxcfg-hwiscsi -j enable <vmhbaX>
e.g.
esxcfg-hwiscsi -j enable vmhba1
You’ll need to reboot to let the changes take effect. To verify run:
esxcfg-hwiscsi -l – lists the current settings.
Useful link: http://www.vi-tips.com/2009/04/configuration-of-iscsi-in-vmware-vi3.html