Editing Backup (section)

===3-2-1 Backup Rule===
The backup data needs to be stored, requiring a [[backup rotation scheme]],<ref name="KissellTakeControlMacOSX" /> which is a system of backing up data to computer media that limits the number of backups of different dates retained separately, by appropriate re-use of the data storage media by overwriting of backups no longer needed. The scheme determines how and when each piece of removable storage is used for a backup operation and how long it is retained once it has backup data stored on it. The 3-2-1 rule can aid in the backup process. It states that there should be at least 3 copies of the data, stored on 2 different types of storage media, and one copy should be kept offsite, in a remote location (this can include [[cloud storage]]). 2 or more different media should be used to eliminate data loss due to similar reasons (for example, optical discs may tolerate being underwater while LTO tapes may not, and SSDs cannot fail due to [[head crash]]es or damaged spindle motors since they do not have any moving parts, unlike hard drives). An offsite copy protects against fire, theft of physical media (such as tapes or discs) and natural disasters like floods and earthquakes. Physically protected hard drives are an alternative to an offsite copy, but they have limitations like only being able to resist fire for a limited period of time, so an offsite copy still remains as the ideal choice.

Because there is no perfect storage, many backup experts recommend maintaining a second copy on a local physical device, even if the data is also backed up offsite.<ref>
Jeph Preece.
[https://web.archive.org/web/20160816162547/http://www.toptenreviews.com/services/internet/best-online-data-backup-services/ "Online Data Backup Reviews: Why Use an Online Data Backup Service?"].
Top Ten Reviews.
2016.
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Kyle Chin.
[https://www.upguard.com/blog/how-to-back-up-your-data "How to Back Up Your Data: 6 Effective Strategies to Prevent Data Loss"].
2024.
</ref><ref>
[https://www.kingston.com/en/blog/personal-storage/how-to-backup-drives-windows-mac "How do you backup your computer? Windows and Mac drive backup"].
2023.
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Scott Gilbertson.
[https://www.wired.com/story/how-to-back-up-your-digital-life/ "How to Back Up Your Digital Life"].
2024.
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