Copyright (C) 2008 Happy Fish / YuQing

FastDFS may be copied only under the terms of the GNU General
Public License V3, which may be found in the FastDFS source kit.
Please visit the FastDFS Home Page for more detail.
Chinese language: http://www.fastken.com/


FastDFS is an open source high performance distributed file system. It's major
functions include: file storing, file syncing and file accessing (file uploading
and file downloading), and it can resolve the high capacity and load balancing
problem. FastDFS should meet the requirement of the website whose service based
on files such as photo sharing site and video sharing site.

FastDFS has two roles: tracker and storage. The tracker takes charge of
scheduling and load balancing for file access. The storage store files and it's
function is file management including: file storing, file syncing, providing file
access interface. It also manage the meta data which are attributes representing
as key value pair of the file. For example: width=1024, the key is "width" and
the value is "1024".

The tracker and storage contain one or more servers. The servers in the tracker
or storage cluster can be added to or removed from the cluster by any time without
affecting the online services. The servers in the tracker cluster are peer to peer.

The storarge servers organizing by the file volume/group to obtain high capacity.
The storage system contains one or more volumes whose files are independent among
these volumes. The capacity of the whole storage system equals to the sum of all
volumes' capacity. A file volume contains one or more storage servers whose files
are same among these servers. The servers in a file volume backup each other,
and all these servers are load balancing. When adding a storage server to a
volume, files already existing in this volume are replicated to this new server
automatically, and when this replication done, system will switch this server
online to providing storage services.

When the whole storage capacity is insufficiency, you can add one or more
volumes to expand the storage capacity. To do this, you need to add one or
more storage servers.

The identification of a file is composed of two parts: the volume name and
the file name.

Client test code use client library please refer to the directory: client/test.

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(Chinese Language): fastdfs

  FastDFS是一款开源的分布式文件系统，功能主要包括：文件存储、文件同步、文件访问（文件上传、文件下载）等，解决了文件大容量存储和高性能访问的问题。FastDFS特别适合以文件为载体的在线服务，如图片、视频、文档等等。

  FastDFS作为一款轻量级分布式文件系统，版本V6.01代码量6.3万行。FastDFS用C语言实现，支持Linux、FreeBSD、MacOS等类UNIX系统。FastDFS类似google FS，属于应用级文件系统，不是通用的文件系统，只能通过专有API访问，目前提供了C和Java SDK，以及PHP扩展SDK。

  FastDFS为互联网应用量身定做，解决大容量文件存储问题，追求高性能和高扩展性。FastDFS可以看做是基于文件的key value存储系统，key为文件ID，value为文件内容，因此称作分布式文件存储服务更为合适。

  FastDFS的架构比较简单，如下图所示：
  ![architect](images/architect.png)

  FastDFS特点如下：
    1）分组存储，简单灵活；
    2）对等结构，不存在单点；
    3）文件ID由FastDFS生成，作为文件访问凭证。FastDFS不需要传统的name server或meta server；
    4）大、中、小文件均可以很好支持，可以存储海量小文件；
    5）一台storage支持多块磁盘，支持单盘数据恢复；
    6）提供了nginx扩展模块，可以和nginx无缝衔接；
    7）支持多线程方式上传和下载文件，支持断点续传；
    8）存储服务器上可以保存文件附加属性。

  FastDFS更多更详细的功能和特性介绍，请参阅FastDFS微信公众号的其他文章，搜索公众号：fastdfs。