MediaGrid Architecture
Slices are controlled and stored by the two largest operational components of the MediaGrid: contentdirectors and contentservers. The former maintain and monitor the flow of content to and from contentservers. Depending on the user's needs, a MediaGrid can include two or three ContentDirectors, and from 12 to hundreds of ContentServers.
One or more ContentDirectors, which control the entire operation of the system, handle all data and access to its storage, while multiple ContentServers offer the storage and bandwidth of content access. Client applications interact with the ContentDirector to request control services such as opening a file, and the ContentDirector refers the client to one or more ContentServer for access.
ContentServers store, monitor this storage, offer the computational requirement that is possible for grid-based applications and maintain constant communication with ContentDirectors, keeping them abreast of system status, size of stored files, etc. When files are recorded in the MediaGrid, they are divided into slices, where each slice is written entirely to a single disc within a content server.
The placement of each of the slices depends on availability, system load, capacity, and server pooling. Each slice of a particular file is stored on a different server, and a replica of each slice is copied to another server. As this replication process is immediate and dynamic, multiple clients can access any slice of any file from any available server, resulting in a completely affordable broadcaster or digital media company, without bottlenecks caused by the high demand for a particular object.
MediaGrid's system, which also makes efficient use of available time, verifies and processes slices that have been removed. This verification process recognizes files that cannot be read or that are invalid and automatically triggers a re-replication of the slice.
