With the USB DSS module you can only overwrite this with our encrypted image. If let's say for some reason your system is struck by an electrical hit and the DSS module was effected you would be able to use the Demo-CD to keep your data and users active. All your information is stored on the USB and on your drives – by saving your settings in Maintenance > Miscellaneous tab. So when a new DSS is shipped you can restore. We have thousands of instillations from Fortune 100 to Military, so I think you are in good hands. By the way MTBF (approx. 2+ million. hrs.) is higher then a HD drive not to mention the extra drive for the OS (if using RAID 1).