As I quickly said in a previous article, backups and archives are different and you may need both. Let me explain.
Purpose of Backup: Be able to do a recovery
The main purpose of a backup is to be able to make a recovery if things go wrong with your main storage. Disks can become unusable or bad events can occur. Even with RAID, there is nothing left if a high voltage surge destroys all the drives. Fires and floods are other examples of events.
When you lose your main storage, you need to recover the data. That’s the purpose of a backup.
Good practices recommend at least something like the 3-2-1 backup (three copies, two different medias, one offsite).
Purpose of Archive: Long term data retention
The main purpose of an archive system is long term data retention. Typically it’s cold data that needs to be kept, that doesn’t need to be accessed often.
Documents that you legally need to keep just in case during a specific period are a good example.
An archive is typically read only (write once). Non re-writable media like CD-R, DVD-R or BD-R (Blu-ray Disc Recordable) may be used for that. Don’t get me wrong, it’s often not the best option.
Using an archive process may help free up some space in your main storage. You don’t want to have SSDs of your production server constantly filled.
Have you seen police series or movies? If you’ve seen some of them produced before the digital age, you may have noticed that the case under investigation is typically on the police officer desk (or inside the drawers of the desk). But they may have an archive room with a lot of carton boxes for closed cases and cold cases. Well my purpose is not to explain to you TV shows or how police work but I hope it helped you to get my point.
Because archived documents are not accessed often, cloud solutions like Amazon AWS S3 Glacier may be used.
But do I need to be able to go back in time with backups?
That’s where things get a little more complicated.
Having two backups, one offsite, and you have something if there is a fire or a flood. However, what is your option if you accidentally delete a file and realize too late? All backups may have the file deleted. Same if a cyber-attack introduces a virus or some data corruption. If all your backups contain the corrupted data, you have a big issue.
That’s where keeping multiple backup images becomes useful. For example, you may keep a few daily backup images, a few weekly images, and a few monthly images.
You may also have your data copied to a system with some kind of versioning or snapshot features. Maybe you’ve heard of Apple Time Machine. Well this is not necessarily the good product for you but I hope you got the idea.
What’s next?
I hope I helped you to grab some basic notions, and to have in mind the various needs you may have. In future articles I’ll go into more practical stuff.