"Reprint" What is Fastdfs?

Fastdfs is an open source lightweight Distributed File system, which manages files, including file storage, file synchronization, file access (file upload, file download), and so on, which solves the problem of large capacity storage and load balancing. Especially suitable for file-based online services, such as photo album sites, video sites and so on. The FASTDFS server has two roles: Tracker (tracker) and storage node (storage). The tracker mainly does the dispatching work, and the function of load balancing on the access. The storage node stores files and completes all the functions of file management: storing, synchronizing and providing the Access interface, FASTDFS simultaneously manages the metadata of the files. The so-called meta data of a file is the relevant property of the file, expressed as a key-value pair (key Valuepair), such as: width=1024, where the key is Width,value 1024. File metadata is a list of file attributes that can contain multiple key-value pairs. Both trackers and storage nodes can be composed of one or more servers. Servers in trackers and storage nodes can be added or offline at any time without impacting online services. All servers in the tracker are peers, and can be increased or decreased at any time depending on the pressure of the server. To support large capacity, storage nodes (servers) are organized in a sub-volume (or grouping) manner. The storage system consists of one or more volumes, and the files between the volumes and volumes are independent of each other, and the cumulative file capacity of all volumes is the file capacity of the entire storage system. A volume can consist of one or more storage servers, and the files in a storage server under a volume are the same, and multiple storage servers in the volume play a role of redundant backup and load balancing. When adding servers to a volume, synchronizing existing files is done automatically by the system, and after synchronization is complete, the system automatically switches the new server to the online service. You can add volumes dynamically when storage space is low or is about to be exhausted. You only need to add one or more servers and configure them as a new volume, which increases the capacity of the storage system. The file ID in Fastdfs is divided into two parts: volume name and file name, both of which are indispensable. Fastdfs File upload uploading files Interactive process: 1. Client asked tracker uploaded to the storage, no additional parameters required; 2. Tracker returns an available storage;3. Client directly and storage communication to complete the file upload. Fastdfs file download Download files interactive process: 1. Client asks tracker to download the file storage, the parameter is the file identification (volume name and file name); 2. Tracker returns an available storage;3. Client direct and Storage communication complete file download. Need to explain theYes, the client is the caller of the Fastdfs service, and the client should also be a server, and its calls to tracker and storage are all server-side calls.

"Reprint" What is Fastdfs?