### Understand the alert

This alert monitors the number of BTRFS read errors on a device. If you receive this alert, it means that your system has encountered at least one BTRFS read error in the last 10 minutes.

### What are BTRFS read errors?

BTRFS (B-Tree File System) is a modern file system designed for Linux. BTRFS read errors are instances where the file system fails to read data from a device. This can occur due to various reasons like hardware failure, file system corruption, or disk problems.

### Troubleshoot the alert

1. Check system logs for BTRFS errors

   Review the output from the following command to identify any BTRFS errors:
   ```
   sudo journalctl -k | grep -i BTRFS
   ```

2. Identify the affected BTRFS device and partition

   List all BTRFS devices with their respective information by running the following command:
   ```
   sudo btrfs filesystem show
   ```

3. Perform a BTRFS filesystem check

   To check the integrity of the BTRFS file system, run the following command, replacing `<device>` with the affected device path:
   ```
   sudo btrfs check --readonly <device>
   ```
   Note: Be careful when using the `--repair` option, as it may cause data loss. It is recommended to take a backup before attempting a repair.

4. Verify the disk health

   Check the disk health using SMART tools to determine if there are any hardware issues. This can be done by first installing `smartmontools` if not already installed:
   ```
   sudo apt install smartmontools
   ```
   Then running a disk health check on the affected device:
   ```
   sudo smartctl -a <device>
   ```

5. Analyze the read error patterns

   If the read errors are happening consistently or increasing, consider replacing the affected device with a new one or adding redundancy to the system by using RAID or BTRFS built-in features.

### Useful resources

1. [smartmontools documentation](https://www.smartmontools.org/)