Several friends and family have asked about backups, so the audience for this is non-software engineers.
Backups are an important part of preserving files. A widely recommended approach for this is the 3-2-1 Backup Strategy. The below sections are ordered by ease of implementation, so I recommend going in that order.
Online File Sync
Online file sync is probably the easiest to get started with. Some examples of file sync services are Google Drive and Dropbox. An app you install on your computer syncs your files to the provider, giving you easy up-to-date access to the files across devices.
The downside of this is that you are dependent on the service provider (which could shut down or lose your files). Additionally, while reputable companies should have strong security controls, the company you use for this service still has access to your files. Also note that these services typically sync all changes, so unless the service maintains copies of previous versions, online file sync is vulnerable to accidental or malicious corruption of your files such as by ransomware. For this reason, some may not consider online file sync to be a true backup.
Online Backup Service
Online backup services such as Backblaze are dedicated to backups. These services are more likely to preserve previous versions of your files (Backblaze does) and more likely to use client-side encryption so that by design the backup service does not have access to the contents of your files. The benefit of these services is that the backup app you install on your computer regularly performs the backup so you do not have to worry about taking time to manually do it.
These services could shut down or lose your files, just as online file sync services. Another consideration for both online file sync and online backups is that restoring all of your files could take a long time, depending on your internet connection speed and how much data you have.
Offline storage means copying files to an external storage device that you then disconnect from your computer and store securely. Offline storage protects your files from ransomware or corruption since the copy you made to the device is untouched while disconnected from your computer. Keep in mind that storage devices can wear out, so it’s a good idea to keep more than one copy.
The two primary challenges with offline storage are maintaining a schedule and knowing what to copy. Quarterly or monthly updates of offline storage could be a good cadence to use, depending on how frequently new files are added. Avoiding procrastion when you get a calendar notification to do the backup will take some dedication with this approach. Next, depending on the amount of data you need to backup, the easiest approach is to simply copy all of the files each time you take a backup. One caveat with this though is that any changes made to the source will be copied (including any deletions or corrupted files) so you should be sure of the integrity of the source files. With this approach, unless your files are very well organized, it is also challenging to make sure you have copied all the files you want. A better approach is to use your OS’s built-in feature for file backups and just target the backup at your external storage; Backblaze has good guides for Mac and Windows.
Also, unless you encrypt the offline copy, anyone with physical access to the disk can read your files. With Mac this is very easy, but with Windows it’s not clear to me how to do this. This post might offer a starting point for Windows users.
Online file sync and online backup services are considered offsite, so your files should survive as long as your computer isn’t destroyed at the same time the online service shuts down or loses your files. Another level to offsite storage you can use if you have already have offline storage is to make one or more additional offline copies and rotate them through a trusted location, such as a friend or family member’s house. Again, keep in mind that unless the disk is encrypted, whoever has physical access to your backups could read your files.