### Understand the alert

This alert indicates that `BTRFS` flush errors have been detected on your file system. If you receive this alert, it means that your system has encountered problems while flushing data from memory to disk, which may result in data corruption or data loss.

### What is BTRFS?

`BTRFS` (B-Tree File System) is a modern, copy-on-write (CoW) file system for Linux designed to address various weaknesses in traditional file systems. It provides advanced features like data pooling, snapshots, and checksums that enhance fault tolerance.

### Troubleshoot the alert

1. Verify the alert

Check the `Netdata` dashboard or query the monitoring API to confirm that the alert is genuine and not a false positive.

2. Review and analyze syslog

Check your system's `/var/log/syslog` or `/var/log/messages`, looking for `BTRFS`-related errors. These messages will provide essential information about the cause of the flush errors.

3. Confirm BTRFS status

Run the following command to display the state of the BTRFS file system and ensure it is mounted and healthy:

```
sudo btrfs filesystem show
```

4. Check disk space

Ensure your system has sufficient disk space allocated to the BTRFS file system. A full or nearly full disk might cause flush errors. You can use the `df -h` command to examine the available disk space.

5. Check system I/O usage

Use the `iotop` command to inspect disk I/O usage for any abnormally high activity, which could be related to the flush errors.

```
sudo iotop
```

6. Upgrade or rollback BTRFS version

Verify that you are using a stable version of the BTRFS utilities and kernel module. If not, consider upgrading or rolling back to a more stable version.

7. Inspect hardware health

Inspect your disks and RAM for possible hardware problems, as these can cause flush errors. SMART data can help assess disk health (`smartctl -a /dev/sdX`), and `memtest86+` can be used to scrutinize RAM.

8. Create backups

Take backups of your critical BTRFS data immediately to avoid potential data loss due to flush errors.

### Useful resources

1. [BTRFS official website](https://btrfs.wiki.kernel.org/index.php/Main_Page)
2. [BTRFS utilities on GitHub](https://github.com/kdave/btrfs-progs)
