Just noticed that the behaviour of Storage vMotion with CBT (changed block tracking) has changed since ESXi 5.5 Update 2.
Using vSphere prior to version 5.5 U2, a Storage vMotion resets CBT.
This is a problem, because backup products like eg. VMware Data Recovery (VDR), vSphere Data Protecion (VDP), Veeam or IBM TSM are using CBT to perform incremental backups.
As a result, after moving a virtual machine via Storage VMotion to another LUN, the backup software performes a full backup instead of an incremental.
With ESXi 5.5 Update 2 this issue is resolved, as you can see in the release notes of vSphere 5.5 Update 2:
If you want to read more about this, take a look at KB 2048201:
Changed Block Tracking is reset after a storage vMotion operation in vSphere 5.x