NVME 1TB cache drive shows as 750GB

[driftking]

Hello, I just installed a brand new nvme 1TB drive as a cache drive and once formatted in unraid it shows up as 750GB for the capacity. Anything I can do to regain the additional storage space?

[ChatNoir]

More details would be needed to provide any informed suggestion.

Please attach your diagnostics to your next post.

 

Was this new drive added to a previously existing pool ? If so, what drives were already in the pool ?

A screenshot of the Pool Devices section of Main could also be informative.

[driftking]

This is a brand new drive out of the box. I replaced my existing 500GB ssd with a 1TB m.2 nvme for the cache drive. As far as I know, the drive was never added to any existing pools.

 

tower-diagnostics-20220218-1459.zip

[JonathanM]

I hate that I don't have the depth of knowledge to confidently advise you on the fully correct solution, but in a nutshell, Unraid incorrectly decided you wanted to add the 1TB and the 500GB together in a RAID1, and because of the limitations of BTRFS RAID1 with different size devices, it's incorrectly reporting a usable size of 750GB instead of the actual 500GB. If you physically remove the 500GB SSD from the machine before telling BTRFS to remove it from the pair, I don't know what will happen.

 

At the moment, even though it's not showing this in the GUI, the system logs seem to clearly state that both drives are participating in the BTRFS cache pool. I believe the solution will be to run a balance command of some sort, check the result to be sure the volume only has the 1 intended member instead of both, and then you should be good.

 

Please wait for someone with a more specific answer if you need to save the data that is currently on the cache pool. If you are comfortable erasing any data on both the 500GB and the 1TB, you can run a blkdiscard command to fully erase both, which should reset Unraid's view after a reboot and allow the single specified device to be formatted correctly.

 

If you want to wait a few hours, @JorgeB should know the exact command needed to straighten things out without erasing data, or if you want to blow things away just use the blkdiscard command pointed at /dev/sdb and /dev/nvme0n1, assuming those are the old and new cache drives. Be VERY sure you use the correct /dev id's, as those can possibly change between power cycles. Just because those are the id's listed in the screenshot you posted, you should verify that those are the correct drives immediately before issuing the command.

 

[driftking]

Thanks for the help @JonathanM, I went in and out of the cache menu and I eventually was able to break apart the pool of the two drives then I was able to erase the 1TB drive and format. The storage space shows correctly now.