I am using BTRFS to create a RAID0 volume from 2 disks. Both are on an AWS EC2 instance with 30 GB space available each. The command I used to create the filesystem is:
btrfs -d raid0 -L MYLABEL /dev/xvdf /dev/xvdg.
Now Ubuntu tells me the disk space is full, just as BTRFS:
root@host:/var/docker-apps/prometheus# btrfs balance start -dconvert=raid0 . ERROR: error during balancing '.': No space left on device There may be more info in syslog - try dmesg | tail root@host:/var/docker-apps/prometheus#
The fun thing is, when I look at
btrfs filesystem usage I get this:
root@host:/var/docker-apps/prometheus# btrfs filesystem usage . Overall: Device size: 60.00GiB Device allocated: 60.00GiB Device unallocated: 2.00MiB Device missing: 0.00B Used: 25.26GiB Free (estimated): 34.22GiB (min: 34.22GiB) Data ratio: 1.00 Metadata ratio: 2.00 Global reserve: 256.00MiB (used: 0.00B) Data,RAID0: Size:57.98GiB, Used:23.76GiB /dev/xvdf 28.99GiB /dev/xvdg 28.99GiB Metadata,RAID1: Size:1.00GiB, Used:766.11MiB /dev/xvdf 1.00GiB /dev/xvdg 1.00GiB System,RAID1: Size:8.00MiB, Used:16.00KiB /dev/xvdf 8.00MiB /dev/xvdg 8.00MiB Unallocated: /dev/xvdf 1.00MiB /dev/xvdg 1.00MiB root@host:/var/docker-apps/prometheus#
Now, for me that reads like "I have 60 GB of RAID0 space available, and I currently use about 25 of them (Used: entry in the top block, together with Free: entry in the same block)". I think this is pretty clear.
No space left on device.
So - am I wrong? How do I have to read this? Why can't I create files in the BTRFS partition any more? How do I have to read this output? What's going on here?