fastDFS分布式文件系统

   最近关注分布式文件系统，看了一下google file system的论文，感想颇多，颠覆传统的文件系统概念，更重要的是性能非常的好，思考之余让我又想起了oracle数据库的机制，又是感慨颇多，让我再次理解了思想是什么，方法是什么。

    闲话少说，对比了一下分布式文件系统，还发现了fastDFS这个轻量级的文件系统也是非常不错的。以下是摘自google中的内容。

FastDFS is an open source high performance distributed file system (DFS). It's major functions include: file storing, file syncing and file accessing, and design for high capacity and load balancing.

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 vidio 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.