Storage vMotion is a component of VMware vSphere that allows the live migration of a running virtual machine's (VM) file system from one storage system to another, with no downtime for the VM or service disruption for end users. This migration occurs while maintaining data integrity.
VMware Storage vMotion begins the process by copying the VM’s metadata , found in its home directory, to the alternate storage location. Next, the software copies the VM’s disk file to the new location using VMware vSphere’s Changed Block Tracking (CBT) functionality to preserve data integrity while the replication occurs. Then CBT module is queried again for a second copy to the new location, this time only of the blocks that have changed since the initial replication had started. This second step persists until both copies are in sync. The VM is then suspended and pointed to the new location of its virtual disk image. Before VMware ESX resumes the VM, the last of the changed regions of the source disk are replicated to the target and the source home directory and disks are removed. The entire process is transparent to the VM and to end users.
Storage vMotion has a variety of uses, including as a migration tool when moving virtual disks off a storage area network (SAN) volume to a newly purchased storage system; as a load balancer; when taking a SAN down for maintenance; and to move virtual disks from the local ESX Server storage to a SAN.
Two vSphere editions, Enterprise and Enterprise Plus, include Storage VMotion. VMware vCenter is also required.