XtreemFS

XtreemFS is an object-based, distributed file system for wide area networks. XtreemFS' outstanding feature is full (all components) and real (all failure scenarios, including network partitions) fault tolerance, while maintaining POSIX file system semantics. Fault-tolerance is achieved by using Paxos-based lease negotiation algorithms and is used to replicate files and metadata. SSL and X.509 certificates support make XtreemFS usable over public networks.
XtreemFS has been under development since early 2007. A first public release was made in August 2008. XtreemFS 1.0 was released in August 2009. The 1.0 release includes support for read-only replication with failover, data center replica maps, parallel reads and writes, and a native Windows client. The 1.1 added automatic on-close replication and POSIX advisory locks. In mid-2011, release 1.3 added read/write replication for files. Version 1.4 underwent extensive testing and is considered production-quality. An improved Hadoop integration and support for SSDs was added in version 1.5.
XtreemFS is funded by the European Commission's IST programme.
The original XtreemFS team founded Quobyte Inc. in 2013. Quobyte offers a professional storage system as a commercial product.