|Full name||Parallel Optimized Host Message Exchange Layered File System|
|Introduced||June 9, 2009 (Linux 2.6.30)|
|Supported operating systems||Linux|
||This article contains wording that promotes the subject in a subjective manner without imparting real information. (December 2012)|
POHMELFS (Parallel Optimized Host Message Exchange Layered File System) is an asynchronous cache coherent distributed file system developed by Russian Linux hacker Evgeniy Polyakov. The current implementation could be seen as a smart and fast replacement of the widely used Network File System (NFS) protocol (which is used to share filesystems between networked computers), with the possibility to use parallelized connections to speed up the transfers. The design roadmap plans to converge it towards a true distributed file system with good scalability, strong fault tolerance and caching.
Key features include local caching of data and metadata, asynchronous processing of almost all events, dynamic (on-line) reconfiguration, full transactions with failover to alternate servers, parallel writes to multiple servers, and strong authentication and encryption. The server runs in user space, and high performance is one of the key design goals.
The main feature still waiting to be implemented (as of June 2009[update]) is to convert POHMELFS to use the Elliptics network project (fault-tolerant distributed hash table object storage) and the Distributed network storage (DST) project, and thus support a fully distributed file system. Another feature on the waiting list is data channel compression between nodes.
The file system design started around November, 2007.
In November, 2008 it's been announced that the file system is going to be redesigned to be a true distributed file system by using the author's new mature projects: DST (Distributed network storage) and the Elliptics network, a fault-tolerant distributed hash table object storage. The result should be a distributed, parallel file system with distributed locking, cache coherency and fault tolerance.
- List of file systems, distributed file systems section
- Comparison of file systems
- Network File System (protocol)