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Why you should always have more than one backup

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What exactly is a backup?


“In IT a backup, or the process of backing up, refers to the copying and archiving of computer data so it may be used to restore the original after a data loss event. The verb form is to back up in two words, whereas the noun is backup”.


The importance of backup is lies in its goal: to ensure that if data is lost or damaged, it can be restored from the stored backup.


Why more than one?


This video; interestingly in the simplest and its non-technical way, describe the importance of having more than one backup: https://www.youtube.com/watch?v=8dhp_20j0Ys.


The story is about Pixar (in 1998); how they almost lost "Toy Story 2" because someone did ‘rm -r -f *’ at the root level of Toy Story 2 project, recursively delete all the child files and folders, in the end almost 90% of the project files get deleted.


They managed to get their backup data restored from tape backup.


But after a week they notice there are some oddities from the restored data. They realize there is a problem with the restored data – most of the pictures rendering process are having error. This part described as “a tricky procedure and very fragile” process.


Turn out that backup was actually busted, which broke its restore result. At that time they are not continuously test their backup result, and they’re never realize there are problem with their backup process.


In the end, a week worth of works are wasted because it was based on the broken restore data.


Luckily somehow Pixar still have another backup; it’s from their Supervisor Technical Director machine that being taken home before (she previously had a maternity leave), because she need to “work from home” during that period.


Her Silicon Graphics workstation just happened to have full “raw” copy of the movie, and during that time it periodically receives incremental update from the server over ISDN network.


In the end one mom’s “home computer” saved Pixar their $100 million team effort of Toy Story 2.


For complete story of this, you can read this article: http://thenextweb.com/media/2012/05/21/how-pixars-toy-story-2-was-deleted-twice-once-by-technology-and-again-for-its-own-good/.


Three is the magic number


The next question will be: how many of “have more than one backup” is enough?


The computer backup rule of three: Backup 3-2-1 rule, can answer the question above.


This rule became a popular concept thanks to Peter Krogh; because, its logical and common sense. He is a well-known photographer who wrote that there are two groups of people: those who have already had a storage failure and those who will have one in the future.


The rule:

  1. Have at least 3 copies of data
  2. Keep these backups on 2 different media
  3. Keep 1 backup offsite


Backup 3-2-1 rule


  1. Have at least 3 copies of data.  In addition to the primary data, there should be at least 2 more backups.
  2. Keep these backups on 2 different media.  Keep copies of data on at least two different storage types, such as internal hard disk drive and removable media (tape, external disk, USB drive, CD/DVD, etc.).
  3. Keep 1 backup offsite.  It’s not a good idea to put all of your Backup data in the same location with the Production data. How difficult it is to recover; if disaster makes your production datacentre completely destroyed, along with your precious backup inside it?





  1. It is (still) considered as best practice because it ensures we'll have a copy of data no matter what happens.
  2. Multiple copies prevent us from losing the only copy of our data.
  3. Multiple locations ensure there is no single point of failure and data is safe from disasters.


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