I'm setting up Unraid for the first time on mostly new hardware. I decided against buying the larger array+parity drives I planned on purchasing because I won't need that capacity until I get BlueIris up and running. For the time being I have 2x 1TB NVME drives I planned to use as mirrored cache drives, and 4x 640gig array drives + 1 640 gig parity drive.

The issue I'm having is I can't start the array because the parity drives are 640 gig and the cache drives are 1tb.

My understanding was the parity drive only backed up the drives in the array, and not the cache drives. Cache drives would offload to the array at some interval.

Is my understanding correct, and is there a supported solution?

Parity doesn't backup anything, it just allows a missing disk to be calculated from parity plus the remaining disks.

 

I've never heard of anyone having cache larger than parity, but it should be allowed since cache is not involved with parity.

 

Are you sure that is the problem and not something else?

 

Go to Tools - Diagnostics and attach the complete diagnostics zip file to your NEXT post.

The parity drive has nothing to do with the cache drive.  But, if the parity drive is even 1 byte less than any data drive (perhaps due to a HPA partition present on it) then the system will do what you're stating.

@Squid - You got it right.  They're all identical make/model disks but one was reading a few bytes lower.  Got it fixed, thanks for your help!