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SLNetworks

Parity vs. Storage

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  • I have two 10TB drives, a 4TB drive, and a 1TB drive.
  • I have one 10TB drive as parity, the other for storage. I wanted to use the 4TB drive as the second parity drive, and the 1TB drive for storage.

 

Unraid says f**k you, invalid configuration. Why? The parity size in total is bigger than the storage available. Wouldn't it make sense to call it valid? Future bug fix maybe? I'm trying to get all my experimenting done before my trial ends.

Edited by SLNetworks

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All parity drives have to be equal or larger than the largest data drive.    So your attempt to use the 4TB drive is not valid as you have a data drive which is 10TB.

 

With 2 parity drives you are supposed to be able to recover from 2 failed drives, but if the configuration you are trying to create was allowed and the 2 10TB drives were to fail then you would not be able recover the failed 10TB data drive.

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7 hours ago, SLNetworks said:

The parity size in total is bigger than the storage available.

Not relevant. Each parity volume is independent, and uses different maths. It's not a matter of capacity, as parity doesn't store any data. Unraid parity recreates entire missing disks, regardless of content.

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As it stands, I have one 10TB drive as parity, one 10TB drive as storage. I would like to add the 4TB drive to the parity, and the 1TB drive to the storage. So yes, my parity would be bigger than my total storage. Unraid says invalid.. greedy bugger.

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While I understand your logic - a 10TB parity drive for a 10TB data drive and a 4TB parity drive for a 1TB data drive - that's just not how unRAID works. It's not a bug, it's by design.

 

If you desire, you could add both the 4TB and the 1TB drive to the array and have 15 TB total data capacity all of which would be protected by the single 10TB parity drive.

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Alright, I understand that. And I see where the 4TB drive becomes invalid. 4 can take care of the 1, 10 can take care of 1, but 4 don't take care of 10. *buries head in cables*

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7 hours ago, SLNetworks said:

Alright, I understand that. And I see where the 4TB drive becomes invalid. 4 can take care of the 1, 10 can take care of 1, but 4 don't take care of 10. *buries head in cables*

The whole idea is that the Parity drive has to be the largest (or equal to the largest) in the array.

 

In your case if you wanted dual parity (and didn't want to buy more drives) then you would need to make both of the 10TB drives parity and then use the 1TB and 4TB for data. This however would reduce your total capacity from 15TB to 5TB.

 

To keep the same size storage as you currently have then you could buy a third 10TB drive for the dual parity.

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Dual parity for a total of four drives is a bit overkill IMHO. Regardless of the size of the drives. 

 

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