Prometheus High disk usage

What is Prometheus High disk usage

Understanding Prometheus

Prometheus is an open-source systems monitoring and alerting toolkit originally built at SoundCloud. It is now a standalone open source project and maintained independently of any company. Prometheus collects and stores its metrics as time series data, i.e., metrics information is stored with the timestamp at which it was recorded, alongside optional key-value pairs called labels.

Symptom: High Disk Usage

One common issue users encounter with Prometheus is high disk usage. This symptom manifests as the disk space on the server running Prometheus filling up rapidly, which can lead to performance degradation or even service outages if not addressed promptly.

Observing the Issue

High disk usage can be observed through system monitoring tools or by directly checking the disk space usage on the server. You might notice that the directory where Prometheus stores its data, typically /var/lib/prometheus, is consuming a significant portion of the available disk space.

Details About the Issue

The root cause of high disk usage in Prometheus is often due to a large amount of time series data being stored. Prometheus stores data in a time series database, and as more metrics are collected over time, the amount of data stored increases. This can be exacerbated by a high cardinality of metrics, long retention periods, or inefficient metric collection practices.

Understanding Time Series Data

Each time series in Prometheus is uniquely identified by its metric name and a set of key-value pairs (labels). The more unique combinations of labels you have, the more time series you will have, which can lead to increased storage requirements.

Steps to Fix the Issue

To address high disk usage in Prometheus, consider the following steps:

1. Reduce Retention Period

Prometheus allows you to configure how long data is retained. By default, Prometheus retains data for 15 days. You can reduce this retention period to decrease disk usage. Modify the --storage.tsdb.retention.time flag in your Prometheus configuration:

--storage.tsdb.retention.time=7d

This command sets the retention period to 7 days. Adjust the value according to your needs.

2. Optimize Metric Collection

Review the metrics you are collecting and ensure that you are only collecting what is necessary. High cardinality metrics can significantly increase storage requirements. Consider using relabeling to drop unnecessary labels or metrics. For more information on relabeling, refer to the Prometheus Relabeling Documentation.

3. Use Remote Storage

If reducing retention and optimizing metrics are not sufficient, consider using remote storage solutions. Prometheus supports remote read and write capabilities, allowing you to offload older data to a remote storage system. Check the Prometheus Remote Storage Integrations for more details.

Conclusion

By understanding the root causes of high disk usage in Prometheus and implementing these strategies, you can effectively manage disk space and ensure the smooth operation of your monitoring system. Regularly review your Prometheus setup and adjust configurations as needed to accommodate changes in your monitoring requirements.