There are several ways to create a good backup of your Mac mini server. Depending on your requirements you could make a backup on-site, off-site or both.
For critical data, it is a good practice to make at least two backups on different locations and via different methods.
The easiest way to create a backup is on an external USB 3.0 drive directly connected to the Mac mini. We do not charge anything to connect a 2.5" USB drive to your Mac mini other than the one-time purchase fee. You can simply request us to connect a USB drive via a ticket or firstname.lastname@example.org - please also let us know what size you need (1TB, 2TB or 4TB)
When your external drive is connected you can simply create a Time Machine backup to the disk. It will automatically create backups for you and maintain an archive.
Time Machine is a great tool for simple backup purposes, however it might take some time to restore a Time Machine backup. Please take into account that in case of emergency you might need to wait a long time before the restoration of a Time Machine backup is finished.
A better option might be to create a bootable backup. This method ensures the fastest recovery when something goes wrong, because we can easily boot up from your external disk. You can then, at a good moment clone your backup disk back to the main drive.
We highly recommend Carbon Copy Cloner (CCC) as backup-software tool. It is very customisable and also maintains a good archive of deleted files.
Although your Mac mini is running in a highly secured environment, with access control and fire suppression systems active, you might still want to have a copy of your critical data in a separate location to protect it from real disaster.
Often an off-site backup is only required as a last resort, and you will use the on-site backup first. Most likely you will only backup your data and not the whole system off-site.
These are some tools we can recommend for off-site backups.
Please consider that restoring data from an off-site backup provider might take long time. Always check at which speeds you can restore items.
Monitor, monitor, monitor
Nothing gives more stress to find out your backup has not been running for several weeks. You risk high chances of data loss if you do not regularly check your backups for consistency. A backup tool like Time Machine or CCC might run into some error and stop making backups. You don't want to find that out too late.
Make sure you configure proper notifications for such errors, or check your backups manually.
Also check if you can restore all your databases, etc. Not all backup methods deal very well with open files. It might be required to first create a database dump and then backup that file.