src/health/guides/btrfs/btrfs_device_read_errors.md
### 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/)