In this review, the author considers currently available methods for storing and looking up files by metadata. Different available solutions were considered and their shortcomings were highlighted. The purpose of this research is to evaluate the current metadata processing methods in order to provide a robust base to build a metadata indexing system for a distributed documents exchange system. Different projects and researches were considered: Luster, WekaFS, Ceph, Gluster, IPFS, HDFS, Spyglass, Smartstore, and Distributed Metadata Search for the Cloud research. It was concluded that all the considered solutions don't fit the requirements of processing documents metadata. In the end, the characteristics of an ideal system for this job were described.