Understanding X raid backup

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ScottJ437 wrote:

I can't seem to wrap my mind around the backup with the xraid. Do I need to back up to another device?

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The short answer is "yes".  RAID isn't enough to keep your data safe. 

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ScottJ437 wrote:

Hello,

 

I have a RN104 with (2) 6 TB, (1) TB and (1) 2TB drive using Xraid I have 8.17TB free. I've set it up as Xraid becuse I figure I will be replacing the 1 & 2 TB drives with 6TB drives in the future. I'm using the device to store all of my media both for streaming and use with video editing. I can't seem to wrap my mind around the backup with the xraid. Do I need to back up to another device? If I am understanding correctly xraid provides backup and thats why I only have 8.17 TB free?

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The capacity rule for XRAID is "sum the disks and subtract the largest"  For you that is (6+6+2+1)-6 or 9 TB.  The NAS (like windows) reports space use in TiB (though it labels it as TB).  1 TB = 1000*1000*1000*1000 bytes.  1 TiB = 1024*1024*1024*1024 bytes.   9 TB is the same as 8.18 TiB.  There is a bit of overhead (which is why you see it reported as 8.17).

Note if you replace the 1 TB with a 6 TB model you'll end up with (6+6+6+2)-6 = 14 TB.  That's about 12.7 TiB

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ScottJ437 wrote:

Do I need to back up to another device? If I am understanding correctly xraid provides backup and thats why I only have 8.17 TB free? Do I need to setup a back up or does the NAS device do this automatically since I set it up as an x raid? I

What RAID lets you do is recover the contents of any disk from the remaining three.  So if a disk fails, you can just replace it with a working one, and the system will reconstruct the lost contents on the replacement drive. 

This is NOT the same as a backup - and there are several scenarios where RAID redundancy won't help you.

For instance

• a second disk can fail while the replacement disk is being rebuilt.  This happens more often than you might think, and the result is that you lose all the data in the volume.
• an unexpected power loss can corrupt the file system - resulting in loss of some or all your data.
• you might delete some files by mistake.
• your home network might be attacked by Ransomware, resulting in loss of all your files.
• A nearby lightning strike can create an electrial surge that damages the NAS and all the disks in it.
• Someone might knock the NAS off it's shelf and damage the disks.

These possibilities (and several others) were all posted here - so they are not hypothetical.

So if your data matters to you, you do need to back it up.  The NAS doesn't do that automatically.  One method (probably the cheapest) is to purchase USB drives, and back up the NAS files to those drives.  Personally I back up my NAS to other NAS, and also do a cloud backup for disaster recovery (fire, flood, theft, etc).