B1200i, VMWare 5.1 and 5.5, iSCSI, Jumbo Frames

I am attempting to setup jumbo frames on my VMWare infrastructure and things went off the rails.

My infrastructure is two HP servers, a DL380 G6 running VMWare 5.5 and an HP ML370 G6 running VMWare 5.1 connected to two Cisco 3560 switches connected to a B1200i. The iSCSI traffic is in its own VLAN. All VM Guests are using the VMNET3 NIC hardware. I enabled an MTU of 9000 everywhere I could find it.

I started booting everything back up beginning with the Drobo first and then the hosts and then the VMs. I noticed that the guests were taking an unusually long time to boot but I figured that was because I booted them too fast. After about 30 minutes I figured something was wrong and shut all the guests down and rebooted one host. It did not fully come back, I could not connect to it via the VMWare client, but I could connect via SSH. Same with the other host. On boot up I noticed my hosts hung a long time at VMWare loading the iscsi kernal module and deltadisk (whatever that is). I tried pinging the Drobo using vmkping and I got no response.

Anyway I am trying to figure out what happened. I changed the MTU on my Drobo back to 1500 and left the MTU everywhere else on 9000 and things booted up just fine. So all signs point to an issue with the Drobo and an MTU of 9000, I’m just not sure what it is.

Has anyone successfully setup jumbo frames on their B1200i?