RAID – Redundant Array of Independent Drives.
Redundant, but independent.  And those two words show why RAID is not a backup system – your hard disks are independent, and redundant, but if one of your hard disks go bust you’re technically covered because of your RAID system. But… what happens if somebody accidentally erases your data?
Or worse, what if a virus infects your HDD?

The last two examples show why RAID is not a backup system. 
RAID esentially makes your hard drives faster and protects you from one single form of data loss, with the idea that you still have a backup system in place. You can withstand the physical failure of one of your hard drives, but you will not withstand a total virus infection of your hard drives.
Ever heard of ransomware? Ransomware would wreck havoc in a RAID system, given that they’re interconnected.
This is why RAID is not a backup system. And far too many system administrators, IT techs and the general population make this mistake and assumption that somehow RAID i a magic pill for all of the data problems. It’s not. It shouldn’t be. It’s not designed to be like that.

RAID is a crucial system in servers, there is no doubt about that. But by overstating it’s capabilities, many companies and IT techs have forgotten to install and use a dedicated server backup system that would protect them in the case of a major treat to their data. And yes, that includes human error as well, because that is a data threat just like viruses are.
There’s also the risk of your RAID controller failing – in which case it might not take you days, but weeks, to recover your files if you don’t have a backup. That only happens in the happy case of you being able to recover those files, because some of the times you’re out of luck and your data is gone.

So repeat after me three times: RAID is not backup. Period!

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