Ubuntu server
3.13.0-24-generic
OS drive is 80GB
The BTRFS drives(/dev/sdb, /dev/sdc) are both 1TB.

So I started playing with BTRFS after playing with ZFS to learn a bit but I think I made a mistake. I ran the following to create the file system-

sudo mkfs.btrfs -d raid1 /dev/sdb /dev/sdc

Now when I run-

sudo btrfs filesystem df /mnt/btrfs/

I get the following output-

Data, RAID1: total=16.00GiB, used=15.24GiB
Data, single: total=8.00MiB, used=0.00
System, RAID1: total=8.00MiB, used=16.00KiB
System, single: total=4.00MiB, used=0.00
Metadata, RAID1: total=1.00GiB, used=17.14MiB
Metadata, single: total=8.00MiB, used=0.00


Reading this (Newb that I am) it appears to have two devices one in raid 1 and one not.

Am I reading this incorrectly or with out the knowledge to properly interpret?

Any knowledge kicked my way would be appreciated.

Looks like this is normal. Thanks to any one who may have pondered this.

Hi gonus,

I noticed that you didn't use the parameter when you created your RAID1 array here. I think that is why you are getting the "single" line; your data is set up as RAID1 but not your metadata. Not sure if you can do this retroactively or not.

I may be wrong but to find free space on a btrfs is a different command.

Yes, it should show a goofy number.
"$ btrfs fi df /mountpoint

will probably report available space in both metadata and data. The problem here is that one particular 256MiB or 1GiB block is full, and wants to allocate another whole block. The easy fix is to run, as root: # btrfs fi balance /mountpoint -dusage=5 "

https://btrfs.wiki.kernel.org/index....complicated.3F

Reading further gives the question, "Why is free space so complicated? "