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XRootD Overview

XRootD is a highly-configurable data server used by sites in the OSG to support VO-specific storage needs. The software can be used to create a export an existing file system through multiple protocols, participate in a data federation, or act as a caching service. XRootD data servers can stream data directly to client applications or support experiment-wide data management by performing bulk data transfer via "third-party-copy" between distinct sites. The OSG currently supports two different configurations of XRootD:


Previously known as the "XRootD proxy cache", XCache provides a caching service for data federations that serve one or more VOs. In the OSG, there are three data federations based on XCache: ATLAS XCache, CMS XCache, and StashCache.

If you are affiliated with a site or VO interested in contributing to or starting a data federation, contact us at

XRootD Standalone

An XRootD standalone server exports an existing filesystem, such as HDFS or Lustre, using both the XRootD and WebDAV protocols. Generally, only sites affiliated with large VOs would need to install an XRootD standalone server so consult your VO if you are interested in contributing storage.