How to make an automatic server with backup on the second disk?

Question

Iron

Good afternoon!
I'm trying to make file storage for family photos, videos, etc.
I'm going to buy two 3TB drives from WD and do a backup without the raidmass. For example, when changing or adding files to disks 1, disk two sees these changes and copies them to itself.
To be honest, I did not find suitable programs for this case. So the question is
1. What program to use to automatically copy from one disk to another.
2. Which cataloger is better to choose.

Answer 1

You need to read about:
- Raid - principles, pros, cons
- alternatives to Raid (for example, StableBit DrivePool https://habr.com/post/193870/)
- Backup - best practices, 3-2-1
The main thing to understand for yourself :
- synchronization of information on two disks protects against the failure of one of these disks, nothing more - it does NOT protect against the failure of both disks (iron due to defective disks \ burning them with a defective PSU \ flooding \ burning; software due to program errors \ viruses\ransomware; erroneous deletion by the user).
- a backup to a separate disconnected disk (preferably more, and geographically distributed) protects against the above, but does not protect against the failure of the backup, which is often found out already when the original failed
- if you do a raid at home, it is unnecessary to do an iron raid or raid using the motherboard, but you need to do a soft-trade, or use a NAS
- therefore, for critical data, they usually do:
- RAID (mirror, RAID5, ZFS RAIDZ, etc.)
- periodic backup to a disconnected external drive - with periodic checks for validity
- remote backup (in the absence of our own remote capacities - to the cloud)
You also need to consider:
- SSD, FLASH are not very suitable for backup, not only because of the price, but also because of the tendency to lose data during long-term storage without power
- CD \ DVD \ BD, etc. optics often do not withstand the stated storage periods even when stored under ideal conditions
- I wrote above about a disconnected disk - if the backup disk is not disconnected from the system, it is vulnerable to software (there is protection against this, for example, Veeam can backup a disk and "disable it "after that, EMNIP), and iron (power combustion).
Those. specifically for your case, you need to understand the budget, I personally have a photo archive:
- on a Synology NAS with their proprietary four-disk raid that protects against the failure of one disk
- in the cloud (flickr)
- on separate disabled NMHD on a shelf