I'm aware of some btrfs issues with full metadata but mine issue seems different.I have 2x3TB disks creating raid0 btrfs filesystem.I can't understand the difference between disk usage reported by:> btrfs fi showLabel: none  uuid: 23a6779e-9c8e-4cec-804b-0056451ab782        Total devices 2 FS bytes used 1009.59GiB        devid    1 size 2.73TiB used 530.02GiB path /dev/sda        devid    2 size 2.73TiB used 530.01GiB path /dev/sdcBtrfs v3.17and> btrfs fi df /mnt/btrfs Data, RAID0: total=1.03TiB, used=1008.49GiBSystem, RAID1: total=8.00MiB, used=96.00KiBSystem, single: total=4.00MiB, used=0.00BMetadata, RAID1: total=2.00GiB, used=1.10GiBMetadata, single: total=8.00MiB, used=0.00BGlobalReserve, single: total=384.00MiB, used=0.00BFrom the first output I presume that my files occupy 530GB from each disk and there is plenty of space still available.But from the second output I see that instead of ~5TB I have only 1TB available and it's almost full (1008.49GiB used)Should I be worried? What is the meaning of this discrepancy?
Discrepancy in disk usage between btrfs fi show and btrfs fi df
debian;filesystems;btrfs
The btrfs FAQ explains what each of these commands is showing.The btrfs fi show command shows the disks in the file system, with the size of each and how much has been allocated on each disk. Your output does not mean that 530 GiB of data are stored, just that this much space has been set aside for data storage. This is also how the regular df command will interpret your filesystem. You are right that there is plenty of space remaining on the devices.The btrfs fi df command provides detail on that allocated space. If you add up all of the total values, accounting for the RAID1 metadata, you will find that you have about the 1060.03 GiB allocated the show command says. The used values are how much information is actually stored in the allocated space for each of those formats.The btrfs fi df command cannot tell you how much more data you can store, because that depends on the formats. 1 GiB of data in single/RAID0 will take 1 GiB of your free space on the filesystem, but 1 GiB of metadata in dup/RAID1 will take 2 GiB of free space on the filesystem. It could tell you how much is free on the disks, but it can't tell you how much will be used for storing data and how much will be used for metadata.