How to competently organize the safety of home server data?

Question

Computer networks

According to the original plan, it was supposed to be a beat-up laptop with 2 HDDs in a mirrored raid array and Debian on board. But a number of jokes about backup made me doubt the expediency of a mirror array in order to increase the safety of data. Plus, the server will be demilitarized, behind its own firewall, which adds risks. But how then to properly organize the idea? How is it done in industrial solutions?
What is the best way to use the resource of two HDDs to increase reliability?
from thoughts:
1) According to the schedule to mount a reserve hard, a backup + check, after to unmount. Not much better from my belfry raid.
2) HDD connected to the router. Something about this option turns me off. A drive that appears as an ftp storage on a home network ... clumsy, or what?
3) What is a very primitive NAS? I don’t really imagine, and it’s expensive + keeping an additional heater in the house is not happy. Although it would be great to find a "dumb" piece of iron that the server could wake up, roll up a backup there, and send it back to sleep.

Answer 1

Backup and backup again.
And you need to approach this with the mind, but without excessive zeal.
A mirror raid does not replace a backup in any way, it is necessary for uninterrupted operation so that work does not stop in the event of a disk failure.
As a replacement for a backup, it is not suitable for the simple reason that it only protects against hardware failure, and not everything, but specifically the disk.
They caught a virus, accidentally deleted a file, wrote down fresh information over the old one - and that's it, the mirror obediently mirrors everything.
Although as an addition to the backup, it is sometimes necessary.

How is it done in industrial solutions?

In industrial solutions, problems are very different, and industrial methods are not applicable to you, both in terms of price and labor costs.
1) Determine what data is valuable.
2) Decide how often to backup, i.e. for what period of time can you painlessly lose data - for a year, for an hour, for a second, for a millisecond?
3) Determine what value the data is for you - that is, how much you are willing to spend to protect it. Agree to hang a $5,000 combination safe lock on a shed with shovels is unreasonable.
Same with backup.
And already clearly knowing these three points - you can develop a backup strategy.

1) According to the schedule, mount the backup hard, backup + check, then unmount it. Not much better from my belfry raid.

Better than a raid, but the problem is that it is located on the same computer, it is better to take it to another machine.

2) HDD connected to the router. Something about this option turns me off. A drive that appears as an ftp storage on a home network ... clumsy, or what?

Not the best option - no speed, and you can't set up security. Better dedicated NAS.

3) What is a very primitive NAS? I don’t really imagine, and it’s expensive + keeping an additional heater in the house is not happy. Although it would be great to find a "dumb" piece of iron that the server could wake up, roll up a backup there, and send it back to sleep.

Already better. As for the heater, it will, in principle, eat no more than a router. The option is close to ideal, if configured correctly.

Answer 2

The first thought is correct.
An inexpensive, but fairly reliable option - there are two screws in the computer.
On the second screw, allocate a place where, according to the schedule, all critical data is backed up, for example, once a day (you can update backups).
Buy a separate external screw, periodically connect and upload the current backup to it, for example, once a month.
So there is a backup copy of everything critical on the second screw, or at least in another place on the screw, plus a backup copy some time ago on the external screw.
If you need something more serious - buy a place in the cloud, and schedule backups to merge there, for example, in the form of a winrar archive with a password or a truecrypt image.