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### Understand the alert
The `btrfs_metadata` alert calculates the percentage of used Btrfs metadata space for a Btrfs filesystem. If you receive this alert, it indicates that your Btrfs filesystem's metadata space is being utilized at a high rate.
### Troubleshoot the alert
**Warning: Data is valuable. Before performing any actions, make sure to take necessary backup steps. Netdata is not responsible for any loss or corruption of data, database, or software.**
1. **Add more physical space**
- Determine which disk you want to add and in which path:
```
root@netdata~ # btrfs device add -f /dev/<new_disk> <path>
```
- If you get an error that the drive is already mounted, you might have to unmount:
```
root@netdata~ # btrfs device add -f /dev/<new_disk> <path>
```
- Check the newly added disk:
```
root@netdata~ # btrfs filesystem show
```
- Balance the system to make use of the new drive:
```
root@netdata~ # btrfs filesystem balance <path>
```
2. **Delete snapshots**
- List the snapshots for a specific path:
```
root@netdata~ # sudo btrfs subvolume list -s <path>
```
- Delete an unnecessary snapshot:
```
root@netdata~ # btrfs subvolume delete <path>/@some_dir-snapshot-test
```
3. **Enable a compression mechanism**
Apply compression to existing files by modifying the `fstab` configuration file (or during the `mount` procedure) with the `compress=alg` option. Replace `alg` with `zlib`, `lzo`, `zstd`, or `no` (for no compression). For example, to re-compress the `/mount/point` path with `zstd` compression:
```
root@netdata # btrfs filesystem defragment -r -v -czstd /mount/point
```
4. **Enable a deduplication mechanism**
Deduplication tools like duperemove, bees, and dduper can help identify blocks of data sharing common sequences and combine extents via copy-on-write semantics. Ensure you check the status of these 3rd party tools before using them.
- [duperemove](https://github.com/markfasheh/duperemove)
- [bees](https://github.com/Zygo/bees)
- [dduper](https://github.com/lakshmipathi/dduper)
5. **Perform a balance**
Balance data/metadata/system-data in empty or near-empty chunks for Btrfs filesystems with multiple disks, allowing space to be reassigned:
```
root@netdata # btrfs balance start -musage=50 -dusage=10 -susage=5 /mount/point
```
### Useful resources
1. [The Btrfs filesystem on Arch Linux website](https://wiki.archlinux.org/title/btrfs)
2. [The Btrfs filesystem on kernel.org website](https://btrfs.wiki.kernel.org)
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