3.7 KiB
| title |
|---|
| BTRFS |
[toc]
Utils
# pacman -S btrfs-progs
Fstab example
UUID=2dc70a6e-b4cf-4d94-b326-0ba9f886cf49 /mnt/tmp btrfs defaults,noatime,compress-force=zstd,space_cache=v2,subvol=@ 0 0
Options:
defaults -> Use whatever defaults
noatime -> Reading access to a file is not recorded
compress-force -> Send all files through the compression algorithm
space_cache -> Increases performance by mapping unallocated blocks
subvol -> Subvolume to mount
Filesystem usage
Show storage allocated, used and free
# btrfs fi usage (mountpoint)
allocated: space used
unallocated: actual free space
Used: amount of data stored
Free: free storage based on "Used"
Start rebalance of datachunks filled less than 70%
# btrfs balance start --b -dusage=70 -musage=70 (mountpoint)
Check status of rebalance
# btrfs balance status -v (mountpoint)
Disable CoW
Disable copy on write for folders (Only works on new files)
$ chattr +C (path)
Device errors
Error counts for a given mountpoint
# btrfs dev stat (mountpoint)
Compression
Algorithms
zlib: Slow, but strong compression, level 1-9
lzo : Fastest, weak compression
zstd: [Recommended] Medium, newer compression standard than the others, only works on newer kernels, level 1-15
Enable compression for existing files
# btrfs filesystem defragment -r -v -c(alg) (path)
It is impossible to specify the level of compression wanted.
Add compress=(alg) to /etc/fstab
To specify a level of compression (zlib and zstd) use compress=(alg):(level) in fstab.
For zstd compression it is recommended to use compress-force=zstd:(level)
Subvolumes
List
# btrfs subv list (path)
Create
# btrfs subv create (path)
Mount a subvolume
# mount -o subvol=@(subvolname) /dev/sdXX /(mountpoint)
Snapshots
TODO
RAID
An array can be mounted by specifying one of its members.
# mount /dev/sdXX /mnt
All members of an array have the same UUID, which can be mounted through fstab.
RAID 1
On filesystem creation
# mkfs.btrfs -m raid1 -d raid1 /dev/sdXX /dev/sdYY
RAID 5
On filesystem creation
It is recommended not to use raid5/6 for metadata yet
# mkfs.btrfs -m raid1 -d raid5 /dev/sdXX /dev/sdYY /dev/sdZZ
RAID 10
On filesystem creation
# mkfs.btrfs -m raid10 -d raid10 /dev/sdXX /dev/sdYY /dev/sdZZ /dev/sdQQ
Convert to single device
First, the files have to be collected on one device.
DUP on system and metadata should only be used on HDDs. Use single on SSDs
# btrfs balance start -f -sconvert=dup,devid=(id) -mconvert=dup,devid=(id) -dconvert=single,devid=(id) /(mountpoint)
Now unused devices can be removed
# btrfs device delete /dev/sdYY /(mountpoint)
Replace dying/dead device in RAID array
Show arrays that are available
btrfs fi show
From my testing the log has to be dropped before btrfs will mount the incomplete array
btrfs rescue zero-log /dev/sdXX
Mount with these options to be able to fix it
mount -o rw,degraded /(mountpoint)
The ID has to be replaced with the ID of the missing device!
btrfs replace start -B (id) /dev/sdYY /(mountpoint)
Query the status of the repace
btrfs replace status /(mountpoint)
Balance the filesystem at the end
btrfs balance /(mountpoint)
Issues
100% CPU Usage
btrfs-transaction and btrfs-cleaner will run on a single cpu core, maxing it out with 100% load.
TODO: Check what enabled quotas in the first place. A likely candidate is snapper
The issue is apparently caused by using quotas in btrfs.
Check if quotas are enabled:
# btrfs qgroup show (path)
Disable quotas:
# btrfs quota disable (path)