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Title: Pohmelfs  
Author: World Heritage Encyclopedia
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Subject: List of file systems
Publisher: World Heritage Encyclopedia


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.

It was announced on January 31, 2008, and merged into the mainline Linux kernel version 2.6.30, released June 9, 2009. It is named after the Russian похмелье (pohmel'e) meaning "hangover".


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) 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.

PohmelFS (as in the original spelling) was born on the date Mon Dec 10 19:38:53 MSK 2007 (Moscow time),[1] and has been released to the public on 31 January 2008.[2]

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.

See also


External links

  • POHMELFS homepage
  • Linux 2.6.30: POHMELFS and DST at Kernel Newbies
  • full transaction support at Kernel Trap
  • CRFS and POHMELFS at Linux Weekly News
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