Statistical disk scheduling for video servers

A queuing architecture for scheduling disk drive access requests in an information video server, comprising, for each disk drive in said information server:

• a first queue for disk access requests from users currently receiving information provided by the information server;
• a second queue for all disk access requests from users requesting new data streams;
• a third queue for all other disk access requests;
• and
• a queue selector for selecting requests from said first and second queues and forwarding said requests to said disk drive.

A method of scheduling access requests for a disk drive in an information server, said method comprising the steps of:

• (a) providing at least two queues, where a first queue contains steady state access requests from users being supplied information from the information server and a second queue for all other types of access requests;
• (b) selecting an access request from said second queue, if such selection does not cause a steady-state request to miss a time deadline within which the steady-state request must be completed to ensure that the information being viewed is not interrupted;
• (c) otherwise, selecting the steady-state request with the earliest time deadline;
• and
• (d) forwarding the selected request to said disk drive.

A method of scheduling access requests for a plurality of disks in a video server, said method comprising the steps of:

• ordering said disk drives by earliest time deadline of steady-state access requests for each of said disk drives;
• and
• for each of said disk drives,
• providing three queues, where a first queue contains steady state access requests from users being supplied a program from the video server, a second queue contains new programming access requests and a third queue for all other types of access requests;
• selecting a next new programming access request, if such selection does not cause any steady-state access request to miss an associated time deadline within which the steady-state request must be completed to ensure that the program being viewed is not interrupted;
• otherwise, selecting a next other access request, if such selection does not cause any steady-state request to miss a time;
• otherwise, selecting a steady-state access request with the earliest time an associated time deadline within which the steady-state request must be completed to ensure that the program being viewed is not interrupted;
• and
• forwarding the selected request to said disk.

A method of scheduling access requests for a plurality of disk drives in a video server, said method comprising the steps of:

• providing, for each of the disk drives in said plurality of disk drives, three queues, where a first queue contains steady state access requests from users being supplied a program from the video server, a second queue contains new programming access requests and a third queue for all other types of access requests;
• determining which of said disk drives has completed a command;
• ordering said disk drives that have completed a command by earliest time deadline of steady-state access requests for said disk drives;
• and
• for each said disk that has completed a command,
• selecting the next new programming request, if such selection does not cause any steady-state request to miss an associated time deadline within which the steady-state request must be completed to ensure that the program being viewed is not interrupted;
• otherwise, selecting the next other-request, if such selection does not cause any steady-state request to miss said associated time deadline within which the steady-state request must be completed to ensure that the program being viewed is not interrupted;
• otherwise, selecting the steady-state request with the earliest time deadline;
• and
• forwarding the selected request to said disk drive.