If you don't have 3 copies on 3 different physical media, then you don't have any backups. That's the rule. And a RAID mirror is counted as 1 copy.
We all start out making ZIP files and calling those "backups". then we often start copying files using a file manager to other storage and call that a "backup". The flaw with these is that we humans are lazy and quickly decide that we just did a backup last week or last month or 8 months ago and that's good enough.
Backup tools exist to make extremely fast and storage efficient backups either daily or weekly. These can be automated, but often, we - being lazy humans - don't bother with the automation part. I had a tape drive, but that was extremely slow, noisy and the tape media wasn't cheap. Because it is a linear storage format, getting back a few files off tape was a hassle too.
In the early 2000s, I was using rsync to mirror all the storage on a system. 1 copy to another HDD. It wasn't automatic, but I did mostly run my rsync script once every 1 or 2 weeks. That became every month, then every 6 months. Life got in the way and I couldn't remember the last time I'd run the script, so I ran it 1 Saturday morning. Talk about lucky. Early, the next Saturday morning that computer was hacked. The hacking method wasn't silent, so I received thousands of notifications by the time I got up to check email. Because I had made a backup (really just 1 mirror) 7 days before, I was able to compare everything between the two disks and see what had changed and what had not changed. It was extremely clear who they'd hacked into the system and where they'd setup their beach to attempt to get more access. I was very lucky. Of course, a few other files had also changed, but I remembered those documents that I'd been editing that week, so those were never a concern. If I didn't have a recent mirror, I'd have been screwed and not been able to trust any of the files, including data files, on the system. Pure luck.
After removing the attacker's beachhead files and patching the program they'd used to get into the system at all, I immediately added my manual rsync script to happen automatically, once a week. rsync is great at all sorts of things, but it really isn't a great backup tool. rsync does about 80% of what a great backup tool should do, but for almost ZERO effort, it isn't hard to setup a real backup tool that does versioning for very little extra storage. 90 days of versioned backups needs just 1.3x the space that a mirror needs. So if you are backing up 100G of stuff, for 90 days of daily, versioned, backups, just 130G of storage is needed (that's an estimate). Doesn't that seem like a bargain? Also, once the first backup is made, all the following backups take just a few minutes. Most of the backups of systems here take less than 2 minutes a day to finish.
I backup about 10 systems every night. The backups for last night started at ....
Code:
INFO: Backup Start: 2024-10-21-00:03:01
and the last backup of the last system ended at ....
Code:
EndTime 1729484549.58 (Mon Oct 21 00:22:29 2024)
A little math says that in less than 20 minutes, I backed up about 10 systems. Again, that seems like a bargain to me.
I've posted example backup scripts here, but back-in-time will easily do about the same thing.
Versioned backups are important for a number of reasons. You can look up why.
