What could go wrong in this picture?
Your church has three portable hard drives that are used to back up the server data. Every day one of your faithful staff dutifully swaps out the portable hard drive and makes a new, complete backup of your server. When a backup is complete, the portable hard drive with the fresh set of backup data is put on the shelf over the server, where it belongs.
What’s the problem?
Well, if the hard drive crashes or the data is corrupted, you can go back to one of the many generations of backups on one of the several portable hard drives and recover usable data.
Let’s say there is a catastrophe in the server room. Perhaps a water leak in the pipes above the server pours water over the server and the portable drives stored above it. Perhaps a small fire in the server room melts all the equipment in that room. Perhaps a thief takes your server and anything else that has obvious value, such as small portable hard drives.
In such a catastrophe, every single one of your backups is gone. (The fire catastrophe is real to me since the office at the church we attend was destroyed in a thief-caused fire several years ago.)
Routinely cycle one of your backup media off-site. The cost of media has dropped so far that it is very simple to have enough backup media that one set can always be offsite.
The best scenario would be storing it in a safe deposit box.
A less expensive approach in dollars and time would be for a highly trusted staff person to take the backup home and then bring back the older backup. Many smaller ministries take this approach.
Another approach, which is easy and cheap now, would be to use an online storage provider. Some of them advertise on the radio frequently. A moment of searching on the Internet will identify a large number of vendors.
Lots of ways to do it, so get a set of your backup data off-site on a regular basis.