# PortSIP PBX High Availability ## PortSIP PBX High Availability Make a high-availability cluster using three PortSIP PBX servers. PortSIP PBX can detect a variety of faults on one PBX server and automatically transfer control to the other server, the established calls will be recovered automatically. **Figure 1-1** PortSIP PBX HA Architecture ![](/files/-MiuZI3nCt3t2M0QjeRq) The Pacemaker is a high availability Cluster Resource Manager (CRM) that can be used to manage resources, and ensure that they remain available in the event of a node failure. [DRBD ](https://linbit.com/drbd/)is used for High Availability purposes. It is a software product used to replicate data in real time from one server to others. This ensures business continuity even in the event of hardware failure. The PortSIP PBX HA using the [Pacemaker](http://www.clusterlabs.org/) to do the resource management and monitoring, once the event of PBX node failure, the resources will automatically move to a working node in the cluster. The DRBD is utilized in the PortSIP HA scenario to synchronize data (DB, recording files, log files, and prompt files) between the PBX nodes. To connect to the PBX service, all SIP clients (IP Phone, Softphone, Mobile App, WebRTC Client) will access the Virtual IP of PortSIP PBX in the HA scenario. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://support.portsip.com/pbx_v12/portsip-uc-high-availability/portsip-pbx-high-availability.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.