Backups are a way more complicated subject than you'd expect. For example, you have the difference between data duplication and a backup, you have to ask how much work you want to do on restoring the backup, you have to decide whether you want to test your backup procedure, you have to decide how long to keep backups for, you have to decide on the types of backups (complete vs incremental), you have to decide how often to do them, you have to decide how often to overwrite previous data / states, you have to decide how off-site you want a backup, etc etc etc... I'm sure Daily can answer better than I can, but for the home user, I see the following scenarios (roughly):
How much data?
- All of it
- All the data, no system state (ie, documents and programs etc but no operating system details)
- All the data, no system state or programs
- Only things that are hard/impossible to restore (large collection of movies and photos, work stuff, etc, no misc stuff)
- Only things that are impossible to restore (or impossible to restore when needed - photos yes, movies no)
- Only important work data
How off-system?
- Copy from one part of the hard drive to another
- Set up a RAID array to mirror (two identical copies) or to stripe-parity (so a single disc can be rebuilt)
- Set up an external device, hard drive or thumb drive or etc
- Set up an external device and store them away from the computer between updates
- Set up an external device and store them off-site, eg, in a storage locker
- Set up external devices and have a real storage company maintain them
- Store using 'cloud' providers, on their servers and hard drives
How fast do you need the data if it needs to be recovered?
- Seconds, minutes, hours, days, weeks, months
How incremental do you need things?
- Overwrite everything, "all my documents today overwrites all my documents from a week ago"
- Just overwrite previous data, eg, your work document replaces the older version of your work document
- Just save entire blobs, eg, "all my documents today in this folder, all my documents from a week ago in this one"
- Incremental backup with versioning, so you can see what changed between backups, eg, you can see your previous versions of your work document
Do you need it encrypted? Are you storing important financial / health data?
How much do you want to pay?
What kind of media? Code backups are different from word documents are different from photos are different from movies etc.
With all that said. I recommend all of the following:
- Back up all important work documents remotely, with versioning, so you can always restore previous versions
- Back up all important photos on free cloud providers and on an external hard drive, they're irreplaceable; periodically make sure the external hard drive can be read
- Don't bother backing up movies and audio you've downloaded, unless you can never find it to download again - or if you really have to, just clone the hard drive to an external one once in a while
- If you can, run a raid array (either mirrored or RAID 5) inside your computer, so you have either two identical drives at all times, or three where one can fail
- Don't worry about things like restore procedures, since you never back up system state; just periodically make sure you can access all the files you've backed up and that they open and display properly
- Don't use things like flash drives or SD cards as long-term backups. External hard drives are okay but make sure they spin up every month or so.