A post on the VMM newsgroup today prompted me to explain the different ways that VMs can be migrated when using VMM 2008.
From a VMM perspective, we have a few ways that we allow you to move a VM from one host to another. I listed them below in no particular order:
-Using Hyper-V and Windows Clustering, we offer what we call "quick migration". This method takes very little time to move a VM from one host to another. This time is proportional to the amount of time required to save the VM state and restore it. Clustering and the Hyper-V cluster resources take care of the rest.
-Using our network migration, we perform a network copy of the data as we move the VM from one host to another. The bulk of the time here is spend on the network copy operation. This is the slowest method of virtual machine migration that VMM offers.
-Using our SAN migration, we allow you to move a VM from one host to another via SAN. For this method, we employ a variety of techniques depending on your storage infrastructure. We can utilitze NPIV (In this case, we migrate a VM from host to host via delete and create vport), iSCSI (in this case, we migrate a VM from host to host via login and logout) or FC (In this case, we migrate a VM from host to host via Storage Array based LUN Masking, utilizing VDS).
-For VMware VMs, we can also utilitize VMotion.
Because of the fact that we move LUNs from one machine to another, we require that for any of the above methods (except VMotion) you need to allocate one VM per LUN. Otherwise we can only migrate a VM via the network migration method.