I have three drives (8TB, 4TB, 3TB). Originally, I created a btrfs partition on the 8TB drive and copied all my data there. I added the 4TB and 3TB drives by using btrfs device add, and then then ran a balance conversion:
btrfs balance start -dconvert=raid1 -mconvert=raid1 /mnt
Now the balance is done, but it still shows some data in "single" and "DUP" mode on the original drive. Here's the output from
btrfs fi usage /mnt/btrfs:
Overall: Device size: 13.37TiB Device allocated: 4.62TiB Device unallocated: 8.75TiB Device missing: 0.00B Used: 4.60TiB Free (estimated): 4.98TiB (min: 4.38TiB) Data ratio: 1.76 Metadata ratio: 2.00 Global reserve: 512.00MiB (used: 0.00B) Data,single: Size:645.00GiB, Used:645.00GiB /dev/mapper/8TB 645.00GiB Data,RAID1: Size:1.98TiB, Used:1.98TiB /dev/mapper/3TB 551.00GiB /dev/mapper/4TB 1.44TiB /dev/mapper/8TB 1.98TiB Metadata,RAID1: Size:8.00GiB, Used:3.84GiB /dev/mapper/4TB 8.00GiB /dev/mapper/8TB 8.00GiB Metadata,DUP: Size:7.00GiB, Used:6.41GiB /dev/mapper/8TB 14.00GiB System,DUP: Size:8.00MiB, Used:400.00KiB /dev/mapper/8TB 16.00MiB Unallocated: /dev/mapper/3TB 2.19TiB /dev/mapper/4TB 2.19TiB /dev/mapper/Seagate_Archive_8TB-btrfs 4.37TiB
- Is there any data which is not stored on more than one disk? So, in other words, is there any data which would be lost if one disk failed? If so, how can I coerce this lingering "single" stored data into RAID1?
- Assuming the "single" and "DUP" data stores are unnecessary, now that everything has been converted to raid, is there any way to clear them up?
Edit: here is some system info:
uname -a Linux 4.8.0-0.bpo.2-amd64 #1 SMP Debian 4.8.11-1~bpo8+1 (2016-12-14) x86_64 GNU/Linux btrfs --version btrfs-progs v4.9
I also should mention that this computer was restarted during the balance, and when it came back up I wasn't able to get the btrfs volume to mount at all (it would just hang). I tried with a number of different mount parameters (skip-param, recovery) and the only one which would work was to mount it read only (using
-o ro). After much frustration, I booted wth an Antergos live USB, which had the newest kernel and btrfs progs on it, and it mounted without a problem. I paused the balance operation which had automatically been started and then booted back into Debian, and it mounted without an issue, so I resumed the balance again.