With VMotion, VM guests are able to move from one ESX Server to another with no downtime for the users. What is required is a shared SAN storage system between the ESX Servers and a VMotion license.
Storage VMotion (or SVMotion) is similar to VMotion in the sense that it moves VM guests without any downtime. However, what SVMotion also offers is the capability to move the storage for that guest at the same time that it moves the guest. Thus, you could move a VM guest from one ESX server’s local storage to another ESX server’s local storage with no downtime for the end users of that VM guest.
Figure 1: Image Source: VMware.com