Grid software components

Each machine contributing resources typically needs to enroll as a member of the grid and install some software that manages the grid’s use of its resources.

Usually, some sort of identification and authentication procedure must be performed before a machine can join the grid. Often certificates, such as those available through Certificate Authorities, can be used to establish and ensure the identity of the donor machine as well as the users and the grid itself.

Some grid systems provide their own login to the grid while others depend on the native operating systems for user authentication. In the latter case, a user ID mapping system may be needed to match the user’s rights properly on different machines. This typically is manually maintained by a grid administrator. He determines which user ID a given user may possess on each grid machine and enters these IDs in a protected database or registry.

In this way, when grid jobs are submitted to different machines for a user, the proper local machine user ID is used for determining the user’s rights.

In some grid systems, it is possible to join the grid without any special authentication. And in others, it is possible for any user to submit jobs to the grid.

Such systems may be convenient to set up, but should be discouraged in larger deployments due to the serious security problems that they would open up. The grid system makes information about the newly added resources available throughout the grid. The donor machine will usually have some sort of monitor that determines or measures how busy the machine is and the rate or amount of resources utilized. This information is “bubbled up” to the management software of the grid and used to schedule use of those resources accordingly. In a scavenging system, this information tells the grid management software when the machine is idle and available for work.

Most importantly, the software installed on a given machine can accept an executable job from the grid management system and execute it. A user somewhere on the grid submits a job for execution on the grid. The grid management software must communicate with the grid donor software to send the job there. The donor grid software must be able to receive the executable file or select the proper one from copies pre-installed on the donor machine. The software is executed and the output is sent back to the requester. More advanced implementations can dynamically adjust the priority of a running job, suspend it, and resume running it later, or checkpoint it with the possibility of resuming its execution on a different machine. These kinds of actions may be necessary to respond to load balancing problems or priority or policy changes in the grid.