btrfs-device man page

btrfs-device — control btrfs devices


btrfs device <subcommand> <args>


btrfs device is used to control the btrfs devices, since btrfs can be used across several devices, btrfs device is used for multiple device management.

Device Management

Btrfs filesystem is capable to manage multiple devices.

Btrfs filesystem uses different profiles to manage different RAID level, and use balance to rebuild chunks, also devices can be added/removed/replace online.

Btrfs filesystem uses data/metadata profiles to manage allocation/duplication mechanism. Profiles like RAID level can be assigned to data and metadata separately.

See mkfs.btrfs(8) for more details.

RAID level
Btrfs filesystem supports most of the standard RAID level: 0/1/5/6/10. RAID levels can be assigned at mkfs time or online.

See mkfs.btrfs(8) for mkfs time RAID level assign and btrfs-balance(8) for online RAID level assign.


Since btrfs is under heavy development especially the RAID5/6 support, it is highly recommended to read the follow btrfs wiki page to get more updated details on RAID5/6: https://btrfs.wiki.kernel.org/index.php…

btrfs-balance(8) subcommand can be used to balance or rebuild chunks to the desired profile.

Due to the fact that balance can rebuild/recovery chunks according to its RAID duplication if possible, so when using RAID1/5/6/10 with some devices failed and you just added a new device to btrfs using btrfs-device(8), you should run btrfs-balance(8) to rebuild the chunks.

See btrfs-balance(8) for more details.

Device add/remove/replace
Device can be added/removed using btrfs-device(8) subcommand and replaced using btrfs-replace(8).

When device is removed or replaced, btrfs will do the chunk rebuild if needed.

See btrfs-replace(8) man page for more details on device replace.


add [-Kf] <dev> [<dev>…] <path>
Add device(s) to the filesystem identified by <path>.

If applicable, a whole device discard (TRIM) operation is performed.


do not perform discard by default
force overwrite of existing filesystem on the given disk(s)
remove <dev> [<dev>…] <path>
Remove device(s) from a filesystem identified by <path>.
delete <dev> [<dev>…] <path>
Alias of remove kept for backwards compatability
ready <device>
Check device to see if it has all of it’s devices in cache for mounting.
scan [(--all-devices|-d)|<device> [<device>…]]
Scan devices for a btrfs filesystem.

If one or more devices are passed, these are scanned for a btrfs filesystem. If no devices are passed, btrfs uses block devices containing btrfs filesystem as listed by blkid. Finally, if --all-devices or -d is passed, all the devices under /dev are scanned.

stats [-z] <path>|<device>
Read and print the device IO stats for all mounted devices of the filesystem identified by <path> or for a single <device>.


Reset stats to zero after reading them.
usage [options] <path> [<path>…]
Show detailed information about internal allocations in devices.


raw numbers in bytes, without the B suffix
print human friendly numbers, base 1024, this is the default
print human friendly numbers, base 1000
select the 1024 base for the following options, according to the IEC standard
select the 1000 base for the following options, according to the SI standard
show sizes in KiB, or kB with --si
show sizes in MiB, or MB with --si
show sizes in GiB, or GB with --si
show sizes in TiB, or TB with --si

If conflicting options are passed, the last one takes precedence.

Exit Status

btrfs device returns a zero exit status if it succeeds. Non zero is returned in case of failure.


btrfs is part of btrfs-progs. Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for further details.

See Also

mkfs.btrfs(8), btrfs-replace(8), btrfs-balance(8)