Reported BTFRS Cache Pool Size Discrepancy After 6.9 Upgrade

[Robin42]

I have a 6 drive BTRFS cache pool in RAID1 with;

4X 500GB drives

1X 4TB drive

1X 2TB drive

 

On the UnRaid dashboard it reports 2.94TB used of 4TB, but on the Main page it report 2.26TB used and 1.10TB free. I've done a rebalance and scrub. What gives? Which one is correct?

 

Before the 6.9 upgrade the numbers matched and I *believe* the 2.26TB used is the correct figure...

[JorgeB]

Used on main should be the correct one, dashboard is still using the old way which was usually wrong for raid1 with different device sizes, if you want post diags to confirm.

[Robin42]

Thanks for the quick and informative reply. does that mean the free size is also the correct on on main? and if so why is the the sum of used and free only 3.36TB instead of 4TB? It also reports the total at 4TB on main.

 

The BTFRS calculator @ https://carfax.org.uk/btrfs-usage/ says it should be 4TB usable with my config, is this no longer correct?

Edited March 4, 2021 by Robin42

[JorgeB]

19 minutes ago, Robin42 said:

Thanks for the quick and informative reply. does that mean the free size is also the correct on on main?

No, free space is usually wrong with different size devices, or with an odd number of same size devices, this is a btrfs issue.