Scalla/xrootd WAN globalization tools: where we are.

The Scalla/Xrootd software suite is a set of tools and suggested methods useful to build scalable, fault tolerant and high performance storage systems for POSIX-like data access. One of the most important recent development efforts has been to implement technologies able to deal with the characteristics of Wide Area Networks, and find solutions in order to allow data analysis applications to directly access remote data repositories in an efficient way. This contribution describes the current status of the various features and mechanisms implemented in the Scalla/Xrootd software suite, which allow to create and efficiently access 'global' data repositories, obtained by aggregating multiple sites through Wide Area Networks. One of these mechanisms is the ability of the clients to efficiently exploit high-latency high-throughput WANs and access remote repositories in read/write mode for analysis-like tasks. We will also discuss the possibilities of making distant data sub-repositories cooperate. The aim is to give a unique view of their content, and eventually allow external systems to coordinate and trigger data movements among them. Experience in using Scalla/Xrootd remote data repositories is also reported.