A virtual machine and its host must meet resource and configuration requirements for the virtual machine disks to be migrated with Storage vMotion.
Storage vMotion is subject to the following requirements and limitations:
Virtual machine disks must be in persistent mode or be raw device mappings (RDMs). For virtual compatibility mode RDMs, you can migrate the mapping file or convert to thick-provisioned or thin-provisioned disks during migration as long as the destination is not an NFS datastore. If you convert the mapping file, a new virtual disk is created and the contents of the mapped LUN are copied to this disk. For physical compatibility mode RDMs, you can migrate the mapping file only.
Migration of virtual machines during VMware Tools installation is not supported.
Because VMFS3 datastores do not support large capacity virtual disks, you cannot move virtual disks greater than 2TB from a VMFS5 datastore to a VMFS3 datastore.
The host on which the virtual machine is running must have a license that includes Storage vMotion.
ESX/ESXi 3.5 hosts must be licensed and configured for vMotion. ESX/ESXi 4.0 and later hosts do not require vMotion configuration in order to perform migration with Storage vMotion.
The host on which the virtual machine is running must have access to both the source and target datastores.
For limits on the number of simultaneous migrations with vMotion and Storage vMotion, see Limits on Simultaneous Migrations in the vSphere Web Client.