I just found a post at techhead.co.uk written by Simon on VMware. The posting is really a guide to performing a basic Storage VMotion using the provided command line method from VMware. There are also other useful bits of information along the way.
As VMware explain in their ‘new features storage guide’:
"Storage VMotion (SVM) enables live migration of virtual machine disks from one datastore to another with no disruption or downtime. Just as VMware VMotion allows IT administrators to minimize service disruption due to planned server downtime, Storage VMotion allows them to minimize disruption by reducing the planned storage downtime previously required for rebalancing or retiring storage arrays. Storage VMotion simplifies array migration and upgrade tasks, and reduces I/O bottlenecks by moving virtual machines while the VM remains up and running. It provides a hot migration of the storage location on which the vmhome resides."
I also found a video on the VMware 2009 Roadmap Video Storage VMotion Enhancements.