VMs with large memory requirements

Hi,

I have a 5 node ESX 5.0 cluster and 2 nodes have additional memory (256GB each) to accommodate 2 large SQL VMs. One (192GB RAM) VM  runs on each of the 2 nodes. My question is how to ensure that both VMs can at least startup and run if one of the 2 "large-memory" nodes is down/offline. Should I just put a memory reservation on those 2 VMs that is less in total than the host memory or will they start up and run anyway?

Thanks,