Mac mini backup

If you mean Disc's as in DVDs, have a look at > Disc Burning Quick Assist

Although note that, the Disc Burning article suggests using an External Hard Drive if you want to backup your entire system.

If you mean Disk as in External Hard Drive, there are several ways.

Simply drag and drop copy your user folders into an External Disk.

Using Time Machine > Mac Basics: Time Machine

Using Disk Utility to make a clone, see > Cloning with Disk Utility FAQ

Using Cloning/Backup software like > Carbon Copy Cloner or SuperDuper.

Your welcome!

While DVDs work OK for small photo libraries and doc's, it is very difficult to split up and save large libraries to Disc media.

I recommend a least one or two good External Hard Drive(s).

If you require hourly backups, then use Time Machine.

If not and you only need a daily, weekly or monthly backup, then use CarbonCopyCloner or SuperDuper.

Glad to help.