> For the complete documentation index, see [llms.txt](https://developer.harness.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.harness.io/resilience-testing/chaos-engineering/chaos-experiments/add-serial-and-parallel-faults.md).

# Add Serial and Parallel Faults

### Prerequisites <a href="#prerequisites" id="prerequisites"></a>

* [What is a Chaos Experiment?](/resilience-testing/chaos-engineering/chaos-experiments/index.md)
* [Chaos Experiments](/resilience-testing/chaos-engineering/chaos-experiments/create-experiments.md)

### Add Serial and Parallel Faults <a href="#add-serial-and-parallel-faults" id="add-serial-and-parallel-faults"></a>

You can add multiple faults in a single chaos experiment that is scaled efficiently by Harness CE during execution.

{% hint style="info" %}
Consider the overall impact that these faults have on the application. Your experience in production environments may differ due to lack of resources when a number of parallel faults are being executed.
{% endhint %}

1. To add a fault that runs in parallel to another fault, point your mouse below an existing fault, and then select **Add**. You can follow the same process to add a serial fault.

   ![Complex Faults Experiment](/files/A3EKt6ROscrA17j0q6K5)

{% hint style="info" %}
For Linux, experiments with a parallel fault are currently not supported.
{% endhint %}

The image below shows a single experiment that consists of serial and parallel faults.

* Faults **A**, **B**, and **C** are parallel faults. They begin execution at the same time.
* Faults **A**, **B**, **C** and faults **D** and **E** are serial. **A**, **B**, and **C** complete execution and then **D** and **E** begin execution.
* Similarly, faults **H** and **I** are serial faults, where **H** completes execution, and **I** begins.

  ![Complex Faults Experiment](/files/3ZiSsb7Prk0XbyA0Jpvu)

### Analyze Experiment <a href="#analyze-experiment" id="analyze-experiment"></a>

You can observe the status of execution of fault/s of a chaos experiment during its run. The screen shows the experiment pipeline on the right hand side, and details such as **Environment**, **Infrastructure Name**, and the runs that have passed and failed on the left hand side.

![Experiment Executing](/files/b9LVQT116atFF1AHLW52)

When the experiment completes execution, it displays the [**Resilience Score**](/resilience-testing/chaos-engineering/chaos-experiments/index.md#determine-the-resilience-of-target-environment-using-resilience-score). This score describes how resilient your application is to unplanned failures. The **probe success percentage** helps determine the outcome of every fault in the chaos experiment. Probes (if any) associated with the experiment are used to understand how the application fared.

![Experiment Failed](/files/B1hPNXXbH8oaG9JVD1qd)

If any of the faults fail, you can find the **Fail Step** that elaborates on the reason why the fault failed.

![Result Fail Step](/files/DrzfV9XsRElHuLYDi71l)

### Next Steps <a href="#next-steps" id="next-steps"></a>

* [Advanced Configuration Settings](/resilience-testing/chaos-engineering/chaos-experiments/advance-configuration-options.md)
* [Run or Schedule Experiment](/resilience-testing/chaos-engineering/chaos-experiments/run-experiments.md)