Depends on what you're doing a bit. Databases? Hypervisors? Just files? If all of the above, its best to use an actual product this. Either foss like borgbackup or Urbackup, or something like Veeam which is a popular pay option.

If its a proxmox hypervisor, they have their own free backup appliance, but you need a second physical server to run it on.

If it's just databases, most have a built in way to take a backup. Just google the name and backup. Make sure it's running automatically and is moved to a separate server on each run.

For files, rsync is a great option.