We got a question this morning on twitter from a customer asking for our best practices for setting up iSCSI storage and vMotion traffic on a VLAN.

The question caused a bit of a discussion here amongst our Tech Support staff and the answer it seems is too long to fit into a Tweet! Instead, here’s what you need to know if you are working on the best design for your VLANS.

iSCSI and vMotion on the same pipe (VLAN) is a big no-no unless you are using multiple teamed 1GbE uplinks or 10GbE uplinks with NIOC to avoid the two stomping on one another.

While vMotion traffic can be turned off/on/reconfigured on the fly, iSCSI traffic does not  handle any changes to the underlying network (though great improvements have been made 5.1/5.5) on the fly. You will need to take a maintenance window to reconfigure how you want your VLANs to function – especially for the iSCSI network – and then (more than likely) perform a rolling reboot of all hosts. If iSCSI traffic is already VLAN’d off, you should just leave the iSCSI traffic where it is as to avoid taking down the whole environment and just move the vMotion network to a separate VLAN.

That said, here is our most recent iSCSI Best Practice Setup guide from Cormac Hogan. Also see: vMotion Best Practice Setup guide.

Here are the pertinent pages in our documentation on the subject:…rking-guide.pdf – Page 187

and…orage-guide.pdf – Page 75