Using RAID 1 as backup?

I understand what RAID 1 is (disk mirroring) - you drop a file and it gets mirrored to the other drive. If one drive fails, your data remains. I understand.

I am planning to use two external HDD as RAID 1 for back-up. However, people on blogs are saying you still need to make a backup of your RAID! I am confused. In that case, aren't you just manually mirroring your data to a third drive? Why do I still need to back-up my RAID? 

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  • Lv 7
    2 months ago
    Favorite Answer

    RAID1 sounds like the perfect backup...except you cannot treat it like a true backup. this is because if you accidentally delete a file, there is no way to recover it, as it is deleted on both drives.

    now, because YOU are using RAID in an EXTERNAL drive, with BOTH drives used for backup, odds are good you won't be deleting anything, so it is not an issue.

    only one recommendation: don't get JUST the size you need. buy twice the size that you need for EACH DRIVE. so if you have 500GB of data, buy 2 1TB drives. this is because of the overhead involved in backing up, plus you always want to be thinking of the future, not just the now...

  • Shadow
    Lv 4
    2 months ago

    The RAID is a file that tells the system what to do with the HDD's. Without that file, the drives will be not be usable in their state of RAID. Why you would want to use RAID for external drives is unknown.

  • 2 months ago

    I would suggest a cloud backup.  This puts a backup off premise and you can enable Versions of files to keep, thus avoiding an accidentally deletion of a file forever.  The off premise helps during the event of a physical disaster in the environment where the server or file share is kept.  Also, VSS file versions can be enabled if you are using Windows and this would help with the accidental deletion scenario.

  • 2 months ago

    If you have two 1 TB drives in a mirror array, you will show a single 1TB drive. If either drive fails, you just replace it. But, what happens if the array itself fails, Then you lose both drives and if they are both being installed at the same time and being equally used, it's actually more likely they could both fail at the same time. This might be why some people are suggesting you back up your RAID.

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  • Anonymous
    2 months ago

    RAID 1 only protects you from hardware failure. It does not protect from viruses deleting your files, ransomware, disk corruption or natural disaster. Depending on how much you need to backup, several companies offer a few gigs of cloud storage for free and provide sync apps. 

  • opurt
    Lv 7
    2 months ago

    As the saying goes, RAID is not a backup.

    Yes, as you point out, with RAID-1 if you copy a file on one drive then it's automatically duplicated on the second drive. The idea is you have 2 drives that act like one so that if one has a hardware failure you can just keep working.

    The issue is that it doesn't just duplicate new or copied files. If you delete a file, the deletion is replicated to the second drive. If a virus infects your files, the infection is replicated to the second drive. That's why you still need a backup, so that you can recover files that have been lost.

  • P
    Lv 7
    2 months ago

    You say you are using two "external" drives for raid which isn't typical and it may not be very ideal depending on how you are hooking them up.  Raid is good security against mechanical failure, which is the most likely cause of loss.  Raid doesn't protect against accidental deletion, virus's, and some types of file corruption.  It's ideal for your boot drive since it can increase read speeds and if one drive fails the computer will stay working.  This is why it's most popular in servers where up-time is critical no matter the cost.  However since some potential issues spread instantly to the mirrored drive it is an inferior form of backup by itself.  Again this often just comes down to how you are using it.  Backups are insurance, and it just depends on how much insurance you really need for the specific files you are backing up.   There's so many inexpensive or free options like Google Photos\drive that allow you to backup your critical files which would make a raid drive be perfectly fine.  Entire computer backups are often unnecessary if your critical files are in the cloud. 

  • 2 months ago

    The RAID system stores everything instantly and all changes are "real time".

    If something gets corrupted or you save the wrong version of a file, that is it - data is lost. There are many possible problems other than disk drive failure.

    A separate backup allows you to recover old versions of files or data from before things going wrong with the primary storage.

    Likewise for such as power glitches that damage the computer/drives.

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