@sfnz Hello again
We have already spoken a little on an earlier state of this post’s topic (per disk allocation) via support email. I think at the time you had 2 disks and had added 2 more but the extra space was not showing up.
As you can see from your
btrfs fi usage /mnt2/storage1/
command btrfs is warning you that some ‘usage’ info is just not working as intended in the parity btrfs raids of 5 & 6.
Hence my suggestion in the email thread and the tool tip during pool creation that it is not an appropriate choice for production (read data you care about).
You will get better results with either raid 1 or raid 10 with
Now as to the figures, and to what you can expect, take a look at the following:
https://carfax.org.uk/btrfs-usage/
Rockstor uses the btrfs device usage mount-point to get the info for the bottom table, ie the per disk Allocation stuff. Note here though that Allocation is not usage. If you look up btrfs allocation system, it basically does raid on a chunk level and then more or less fills these chunks with data. You could have a completely allocated drive that has many many partially occupied chunks. Usually a balance will collect the free spaces and drop chunks that are then no longer needed. But again we come back to the parity raids. That “btrfs fi usage” command givens the following output:
WARNING: RAID56 detected, not implemented WARNING: RAID56 detected, not implemented WARNING: RAID56 detected, not implemented
then goes on to say the whole device is 14 TB which is of course untrue. But Rockstor shows 7 TB. So this is all out of wack. I would suggest that you not use the parity raids and report your experience with the raid1 / 10 variants and we can take it from there. As while the parity btrfs side is sill outputting inconsistent info such as your 2 commands we are in a difficult position to asertain exactly what is happening. Note also that btrfs raid 1 will only do 2 copies of the data and meta data irispective of the number of disk, it does raid / chunk, so it just makes sure that the 2 raid 1 say chunks are on 2 different devices.
We are undergoing a move to a ‘Built on openSUSE’ offering where many of these issues associated with our now rather old kernel and btrfs-progs are already sorted. So we hope in the future to offer better reporting as a consequent of this move. But for the time being I’d not use the parity raids. They are far younger within btrfs than the raid1 / 10 variants and it particularly shows in our use of older in kernel btrfs and tools, in our current CentOS offering. But as stated we are far along the path to being able to do better here.
Hope that answers your question, at least in part. But the key here is that Rockstor is likely slightly confused by the “WARNING: not implemented” output and the inconsistent reporting at the command line. But our focus is now more on moving to our openSUSE variant where, due to upstream btrfs maintenance and backports, we have a better set of legs to stand on.
See the following post by @Flox re openSUSE btrfs back-ports: