As an IT guy who worked with this stuff, I can say for certain that anytime you see some nonsense about how government data was lost because a hard drive failed, it's either an outright lie, or someone was doing something totally illegal (like HRC) and not keeping official records on government servers.
One person's data/email does not live on one disk. It lives, with other people's data, on several disks, with at least enough redundancy for two disks to fail at the same time and still not lose any data. And on most, if not all devices (and I'd have to assume all that are eligible to be sold to government agencies, you CAN'T even delete or overwrite data. It may look like it to the user, but an admin can go retrieve the old copies. When you set up these devices, you configure it to not allow erasure for, say, 7 years. You can increase that, but NEVER decrease it. No one can. If you must destroy data early, you would simply have to buy a new one, copy the data you want to keep, and physically destroy the old unit. And, of course, there are requirements that you have copies at another location.
Along with keeping the data secure from people who shouldn't see it, the above is one of the big reasons why you're not allowed to use a personal server in your bathroom -- so that people CANNOT "lose"/destroy records which have retention requirements.
