MogileFS 2.20

MogileFS is an open source distributed filesystem. MogileFS is not:
- POSIX Compliant -- you dont run regular Unix applications or databases against MogileFS. Its meant for archiving write-once files and doing only sequential reads. (though you can modify a file by way of overwriting it with a new version)
- Completely portable ... yet -- there still is some Linux-ism in the code, at least in the HTTP transport cod, but the plan is to scrap that and make it portable

Main features:>
- Application level -- no special kernel modules required.
- No single point of failure -- all three components of a MogileFS setup (storage nodes, trackers, and the trackers database(s)) can be run on multiple machines, so theres no single point of failure. (you can run trackers on the same machines as storage nodes, too, so you dont need 4 machines...) A minimum of 2 machines is recommended.
- Automatic file replication -- files, based on their "class", are automatically replicated between enough different storage nodes as to satisfy the minimum replica count as requested by their class. For instance, for a photo hosting site you can make original JPEGs have a minimum replica count of 3, but thumbnails and scaled versions only have a replica count of 1 or 2. If you lose the only copy of a thumbnail, the application can just rebuild it. In this way, MogileFS (without RAID) can save money on disks that would otherwise be storing multiple copies of data unnecessarily.
- "Better than RAID" -- in a non-SAN RAID setup, the disks are redundant, but the host isnt. If you lose the entire machine, the files are inaccessible. MogileFS replicates the files between devices which are on different hosts, so files are always available.
- Flat Namespace -- Files are identified by named keys in a flat, global namespace. You can create as many namespaces as youd like, so multiple applications with potentially conflicting keys can run on the same MogileFS installation.
- Shared-Nothing -- MogileFS doesnt depend on a pricey SAN with shared disks. Every machine maintains its own local disks.
- No RAID required -- Local disks on MogileFS storage nodes can be in a RAID, or not. Its cheaper not to, as RAID doesnt buy you any safety that MogileFS doesnt already provide.
- Local filesystem agnostic -- Local disks on MogileFS storage nodes can be formatted with your filesystem of choice (ext3, XFS, etc..). MogileFS does its own internal directory hashing so it doesnt hit filesystem limits such as "max files per directory" or "max directories per directory". Use what youre comfortable with.