# Adding a new driver Pentaho connects to Hadoop clusters using a compatibility layer called a driver. These drivers are Apache Karaf archive files (`.kar` format) that connect Pentaho services to Hadoop clusters. You must use a driver to connect each vendor and version of your Hadoop clusters for the following Pentaho products: * PDI client * Pentaho Server * Analyzer * Interactive Reports * Pentaho Report Designer (PRD) * Pentaho Metadata Editor (PME) Pentaho ships with an Apache Hadoop driver. For specific vendor drivers, visit the [Support Portal](https://support.pentaho.com/hc/en-us) to download the drivers. Install the drivers on the PDI client or [Pentaho Server](/install/10.2-install/pentaho-configuration/tasks-to-be-performed-by-an-it-administrator/set-up-the-pentaho-server-to-connect-to-a-hadoop-cluster/install-a-driver-for-the-pentaho-server.md) before using them. See the **Pentaho Data Integration** document for instructions on installinh a driver on the PDI client. When drivers for new Hadoop versions are released, you can add them to Pentaho, then install them to connect to the new Hadoop distributions. **CAUTION:** When you add a driver, it is loaded into the runtime cache. There are several best practices for adding drivers to the runtime cache. * If you add multiple drivers, you need to allocate 8 to 10 GB of disk space for each driver to your runtime cache. * If you are running an environment that manages multiple instances (executions) of the PDI engine, then allocate enough space for each runtime cache. For example, environments running 50+ concurrent instances require 75GB or more of cache space during peak processing times. --- # 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://docs.pentaho.com/install/10.2-install/pentaho-configuration/tasks-to-be-performed-by-an-it-administrator/set-up-the-pentaho-server-to-connect-to-a-hadoop-cluster/adding-a-new-driver-to-pentaho.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.