This tech has been in existence since the 90's. Basically, it just switches between the two hdd on which will be the master drive thus making it to boot first. The disadvantage, it does not really reduce mechanically wear on the standby hdd since it also consistently run. What I will do if I have this is to install a power switch for my standby hdd (since I have a stby hdd with an image of the os hdd) so I can turn if off until I have the need for it. Of course, if you just use it to have different os's or different users it will be perfect.