First, why do you want to create snapshots? As a FYI, they are not to be used for a b/u solution...only for updating VMs (use snapshots as a restore point in case of VM corruption after performing updates, etc.).
If you want a b/u solution, with ESXi you are very limited in what you can do. You can use Veeam FastSCP (
http://www.veeam.com/vmware-esxi-fastscp.html) to make copies of your VMs, but you have to power down your VMs to do so. The same with using WinSCP (
http://winscp.net/eng/download.php)
.
Regards,
~coolsport00