How much storage is lost in double parity?

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1 disk. In unRaid, each parity disk is 1 whole disk equal or greater in size than than the data disks. So if you have 6 2T drives with one parity, one (2T) would be used for parity, and 5 (10T) would be available for data. If you used dual parity, 2 (4T) woudl be used for parity, and 4 (8T) would be for data. 


With that few drives, unless they are old or unreliable, I'd go with single parity in that size server. Better yet, use single parity and use one of the drives for backups that you keep offsite.

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1 hour ago, shortsyoungster said:

I also have a 4tb hard drive, would it be possible to add that in, or do my parity drives have to be the same size of my largest drive? And yes these are drives I already own. 


Parity has to be at least as large as the largest data drive in the array. You could certainly have a 4T parity, with 2T drives. You'd be all set to add another 4T drive in the future. But until then, 2T of its capacity wouldn't be providing any value.


Take a look at this video as it might help you understand how parity works.




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