Increasing distributed storage survivability with a stackable RAID-like file system

We have designed a stackable file system called Redundant Array of Independent Filesystems (RAIF). It combines the data survivability properties and performance benefits of traditional RAIDs with the unprecedented flexibility of composition, improved security, and ease of development of stackable file systems. RAIF can be mounted on top of any combination of other file systems including network, distributed, disk-based, and memory-based file systems. Existing encryption, compression, antivirus, and consistency checking stackable file systems can be mounted above and below RAIF, to efficiently cope up with slow or unsecure branches. Individual files can be distributed across branches, replicated, stored with parity, or stored with erasure correction coding to recover from failures on multiple branches. Per-file incremental recovery, storage type migration, and load-balancing are especially well suited for grid storages. In this paper, we describe the current RAIF design, provide preliminary performance results and discuss current status and future directions.