Medical information systems could benefit from electronic health records management using openEHR. On the other hand, such a standard adds an additional software layer to the system, which might impact performance. In this article, we present an in-depth comparison of open-source openEHR servers and propose tools for testing them. Load tests for selected opensource servers were prepared using Apache JMeter. Statistics of elapsed time of requests and throughput of each solution were calculated. Results show that open-source openEHR servers significantly differ in performance and stability and prove that load testing should be a crucial part of a development process.