FREE TUTORS ABOUT THE IEEE 1244 STANDARD FOR REMOVABLE MEDIA MANAGEMENT SYSTEM ARCHITECTURE

FREE TUTORS ABOUT THE IEEE 1244 STANDARD FOR REMOVABLE MEDIA MANAGEMENT SYSTEM ARCHITECTURE

As early as 1990, the IEEE Computer Society set up the 1244 project for the development of standards for storage systems. The Storage System Standards Working Group was also established with the objective of developing a reference model for mass storage systems (Mass Storage System Reference Model/MSSRM). This reference model has significantly influenced the design of some storage systems that are in use today. The model was then revised a few times and in 1994 released as the IEEE Reference Model for Open Storage Systems Interconnection (OSSI). Finally, in the year 2000, after further revisions, the 1244 Standard for Media Management Systems was released. This standard consists of a series of documents that describe a platform-independent,distributed management system for removable media. It also defines both the architecture for a removable media management system and its interfaces towards the outside world. The architecture makes it possible for software manufacturers to implement very

scalable, distributed software systems, which serve as generic middleware between application software and library and drive hardware. The services of the system can thus be consolidated in a central component and from there made available to all applications. The specification paid particular attention to platform-independence and the heterogeneous environment of current storage networks was thus taken into account mazingly early on. Systems that build upon this standard can manage different types of media. In addition to the typical media for the computer field such as magnetic tape, CD, DVD or optical media, audio and video tapes, files and video disks can also be managed. In actual fact, there are no assumptions about the properties of a medium in IEEE 1244- compliant systems. Their characteristic features (number of sides, number of partitions, etc.) must be defined for each media type that the system is to support. There is a series of predefined types, each with their own properties. This open design makes it possible to specify new media types and their properties at any time and to add them to the current system. In addition to neutrality with regard to media types, the standard permits the management of both automatic and manually-operated libraries. An operator interface, which is

also documented, and with which messages are sent to the appropriate administrators of a library, serves this purpose. In the following sections we wish to examine more closely the architecture and functionality of a system based upon the IEEE standard.

 Media management system architecture

The IEEE 1244 standard describes a client/server architecture (Figure 9.9). Applications such as network back-up systems take on the role of the client that makes use of the services of the removable media management system. The following components are individually defined:

 • a media management component, which serves as a central repository for the metadata and provides mechanisms for controlling and co-ordinating the use of media, libraries and drives;

• a library manager component, which controls the library hardware on behalf of the media manager and transmits the properties and the content of the library to the media manager;

• a drive manager component, which manages the drive hardware on behalf of the media manager and transmits the properties of the drives to the media manager. In addition, the standard defines the interfaces for the communication with these components:

• the Media Management Protocol (MMP) for the communication between application (client) and media manager (server);

• the Library Management Protocol (LMP) for the communication between library manager and media manager;

• the Drive Management Protocol (DMP) for the communication between drive manager and media manager.

These protocols use TCP/IP as the transport layer. As in the popular Internet applications HTTP, FTP or SMTP, commands are sent via TCP/IP in the form of text messages. These protocols can be implemented and used just as simply on different platforms. The advantage of this approach is that the media manager can implement components as a generic application, i.e. independently of the specific library and drive hardware used. The differences, in particular with the control, are encapsulated in the library manager or drive manager for the hardware in question. For a new tape library, therefore, only a new library manager component needs to be implemented that converts the specific interface of the library into the library management protocol, so that this can be linked into an existing media manager installation. The next sections describe how communication takes place between clients and servers and how the media manager processes the commands.