Today I noticed that I lost approximately 1 TB of very old movies in my collection. I have no idea how it happened, but [Munin](http://munin-monitoring.org/) shows what happened. I'm pretty sure it was my fault. (I was awake at that hour, yes; but, I am not 100% sure.) How can I prevent something like that from happening again? How can I prevent myself (or a program/script) from deleting more than x GB of data? Any suggestion is welcome.
![Munin - Disk usage](https://i.stack.imgur.com/70JHi.png)