Data backups
Important files should be backed up so that a hardware or software failure or careless usage by oneself does not render these files permanently inaccessible. It is easy to keep smaller files (e.g. documents) in a cloud storage so that you don't have to handle backups yourself. Of course, it is advisable to familiarize yourself with the terms of service to see if the cloud service provider actually provides some guarantees on the availability of data.
For an individual, backing up large files to a cloud storage might not be feasible as uploading data can take a lot of time and monthly storage fees apply. Here, using a special software to back up data to either an external or network drive might be better idea. Of course one can handle backups manually by periodically copying important files to external drive, but using a special software has some advantages:
- Speed - instead of copying all files over to the backup drive, only files that have changed since the last backup are updated. This is called incremental backup.
- A couple of last versions (revisions) are kept from each file, so it is possible to undo your changes.
- Backups are done automatically or the user is notified if a new backup needs to be done.
Backing up data is so important that most of the operating systems have some backup tools built in. In Windows, there is Backup and Restore (Windows Vista and 7) or File History (Windows 8, 8.1 and 10). These let the user choose which folders to back up, but the user can also choose to let Windows decide. Backups are created automatically to an external drive when it is connected to the computer or the user is notified to connect the drive from time to time. In Professional and Ultimate versions, it is also possible to back up to a network drive.
In Mac OS X there is Time Machine that automatically back up all files (user defined excludes are possible) to an external or network drive.
As there are many different Linux distributions, there is also no single backup software. Some distributions may have some backup software bundled, but mostly it is up to the user to choose one. For example, Flexbackup can be used for automatic incremental backups, or rsync for manually creating a backup system.
It is important to know that every backup system must be tested for data restore from time to time. Even years worth of backup is useless if the files cannot be restored when needed!
Long-term data retention
Most data storage media eventually wears out when used. Data on storage media can become corrupted because of surrounding environment: humidity, temperature, radiation and salts. Moreover, technology evolves so rapidly that data storage media may become unreadable because:
- there are no devices to work with that type of media
- there are no compatible connections to connect the storage device with
- no drivers are maintained that work with these storage devices
- no maintained software can read or write this storage media anymore
Some examples:
- 3,5" floppy disks
- video cassettes
- console game cassettes
- many new computers do not have optical drives (CD/DVD)
- many tablets do not have USB host ports
In Estonia, National Archives also deals with preserving digital documents and thus has a long-term data retention policy. For example, text documents are archived in either plain text, XML or PDF format. Images are archived in TIFF or PNG format, sound in uncompressed WAV and videos in MPEG (source, in Estonian).
More information about the life span of different storage media can be found from: here and here. There is also a nice illustration about the estimated lifespan of media. 
source https://www.crashplan.com.