It would appear that this cannot be done - at least not easily.  Luckily I had enough storage space left is my Performance pool so that I could duplicate the current performance LUN, and assign it to SPB.  I then did a storage vMotion on all of my "performance" servers, and when everything was complete I removed the old performance LUN that was attached to SPA.  All-in-all it was painless, if somewhat time-consuming.
Hello,  I should start by saying that I have inherited storage responsibilities at my company and I do not have any training with EMC products.  Sorry if my questions are poorly phrased.  We have a dual SP array, which is being used via iSCSI for our VM hosts.  There are two switches on this iSCSI network, so I'm assuming that my predecessor had planned to configure this for failover scenarios at some point.  The problem is, we are only using one ethernet port on SPA for both of our VM hosts (~20 servers between the two) on the iSCSI network.  SPB wasn't configured at all.  After reading through the high-availability document for the VNXe, I have now configured SPB with 2 IP addresses.  eth2 is connected to switch1 and eth3 is connected to switch2.  I have verified the path on my VM Hosts.  My question is, is there a way I can migrate one or more of my datastores over to SPB to balance the load a bit?  I can't seem to find any documentation on how to do this.  Also, can anyone recommend a good place to start for me to get some formal training on the CLI or Unisphere?  Even if it's just self-motivated reading, I'm game.  Thank you!
Change Storage Server/Processor for Datastore on VNXe3150