Video file server maintaining sliding windows of a video data set in random access memories of stream server computers for immediate video-on-demand service beginning at any specified location

• US 5,933,603 A
• Filed: 06/10/1996
• Issued: 08/03/1999
• Est. Priority Date: 10/27/1995
• Status: Expired due to Term

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Vahalia, Uresh K., Tzelnic, Percy, Forecast, John
• Primary Examiner(s): Lim, Krisna
• Assistant Examiner(s): Barot, Bharat
• Application Number:
  US08/661,053
• Time in Patent Office: 1,149 Days
• Field of Search: 395/200.01, 395/200.03, 395/200.08, 395/200.09, 395/200.06, 395/200.3, 395/200.31, 395/200.33, 395/200.36, 395/200.47, 395/200.48 , 395/200.49, 395/200.55-59, 395/200.6, 348/6-8, 348/12-13, 455/4.2, 455/5.1, 711/100, 711/105
• US Class Current: 709/225
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2212/312 In storage controller
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/612 for unicast
• CPC Class Codes: H04L 65/80 Responding to QoS
• CPC Class Codes: H04L 67/01 Protocols
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 67/2885 Hierarchically arranged intermediate devices, e.g. for hierarchical caching
• CPC Class Codes: H04L 67/5681 Pre-fetching or pre-delivering data based on network characteristics
• CPC Class Codes: H04N 21/2182 involving memory arrays, e.g. RAID disk arrays RAID arrays per se G06F3/0689; use of parity to protect data in RAID systems G06F11/1008
• CPC Class Codes: H04N 21/23106 involving caching operations prefetching while addressing of a memory level in which the access to the desired data or data block requires associative addressing means within memory systems or architectures G06F12/0862; caching at an intermediate stage in a data network H04L67/568
• CPC Class Codes: H04N 21/2396 characterized by admission policies admission control, resource allocation in open networks H04L12/5692; arrangements for network security using user profiles for access control H04L63/102; access security in wireless networks H04W12/08
• CPC Class Codes: H04N 21/47202 for requesting content on demand, e.g. video on demand
• CPC Class Codes: H04N 21/816 involving special video data, e.g 3D video
• CPC Class Codes: H04N 7/17318 Direct or substantially direct transmission and handling of requests
• CPC Class Codes: H04N 7/17336 Handling of requests in head-ends

Abstract

A video file server includes an integrated cached disk array storage subsystem and a plurality of stream server computers linking the cached disk storage subsystem to a data network for the transfer of video data streams. The video file server further includes a server controller for applying an admission control policy to client requests and assigning stream servers to service the client requests. The stream servers include a real-time scheduler for scheduling isochronous tasks, and supports at least one industry standard network file access protocol and one file access protocol for continuous media file access. The cached disk storage subsystem is responsive to video prefetch commands, and the data specified for a prefetch command for a process are retained in an allocated portion of the cache memory from the time that the cached disk storage subsystem has responded to the prefetch command to the time that the cached disk storage subsystem responds to a fetch command specifying the data for the process. The time between prefetching and fetching is selected based on available disk and cache resources. The video file server provides video-on-demand service by maintaining and dynamically allocating sliding windows of video data in the random access memories of the stream server computers.

Claims

1. A method of operating a video file server to provide video-on-demand service to clients in a data network so that a client can obtain immediate isochronous access to a video data set beginning at any specified location within the data set, said video file server having a plurality of stream server computers, each stream server computer having at least one data link for isochronous streaming of data from the data set to more than one of said clients, said each stream server computer having a random access memory for storing a respective portion of the data set so that at any time the entire data set is stored in the random access memories of the stream server computers, wherein the method comprises the steps of:

(a) maintaining the respective portion of the data set in the random access memory of said each stream server computer as a sliding window into the data set by loading new data into the respective portion of the data set in the random access memory of said each stream server computer at approximately a rate at which data are isochronously streamed to the clients for viewing, wherein at any time the entire data set is stored in the random access memories of the stream server computers but the entire data set is not stored in the random access memory of any one of the stream server computers and the respective portion of the data set in said each stream server computer partially overlaps the respective portion of the data set in another one of the stream server computers; and

(b) servicing a request of the client for viewing of the data set beginning at the specified location in the data set by establishing a data link to the client from a selected one of the stream server computers currently having in its random access memory a respective portion of the data set including the specified location in the data set, and transferring video data over the data link from the random access memory of the selected one of the stream server computers to the client.

2. The method as claimed in claim 1, wherein the video data set is a movie.

3. The method as claimed in claim 1, wherein the respective portion of the data set in the random access memory of said each stream server computer is maintained as a simple circular queue.

4. The method as claimed in claim 1, wherein the new data are fetched from a storage subsystem for the loading of the new data into the respective portion of the data set in the random access memory of said each stream server computer at approximately the rate at which data are isochronously streamed to the clients for viewing.

5. The method as claimed in claim 1, wherein said loading, of the new data into the respective portion of the data set in the random access memory of said each stream server computer, is performed by transferring the new data between the respective portions of the data set in the random access memories of the stream server computers.

6. The method as claimed in claim 1, wherein said loading, of the new data into the respective portion of the data set in random access memory of said each stream server computer, is performed by transferring the new data to the respective portion of the data set in the random access memory of said each stream server computer from the respective portion of the data set in the random access memory of another one of the stream server computers.

7. The method as claimed in claim 1, wherein video data for the entire data set are transferred from the random access memory of the selected stream server computer to the client, without reassigning the client to another stream server computer.

8. The method as claimed in claim 1, wherein video data for the entire data set are transferred from the random access memory of said each stream server computer to multiple clients simultaneously.

9. The method as claimed in claim 1, wherein some random access memory of the stream server computers is held in reserve and is not needed for storing the entire data set in the random access memories of the stream server computers, and when a stream server computer becomes highly loaded by client requests, reserve memory in another stream server computer is allocated to store a duplicate of a respective portion of the data set in the stream server computer that is highly loaded, the reserve memory in said another stream server computer being allocated in response to a client request for isochronous access to the respective portion of the data set in the stream server computer that is highly loaded, said client request for isochronous access to the respective portion of the data set in the stream server computer that is highly loaded being serviced by said stream server computer that is highly loaded by isochronously streaming data from the random access memory of the stream server computer that is highly loaded, the reserve memory being allocated to provide service for possible additional client requests for isochronous access to the respective portion of the data set in the stream server computer that is highly loaded.

10. A video file server for providing video-on-demand service to clients in a data network so that a client can obtain immediate isochronous access to a video data set beginning at any specified location within the data set, said video file server comprising, in combination:

a plurality of stream server computers, each stream server computer having at least one data link for isochronous streaming of data from the data set to more than one of said clients, said each stream server computer having a random access memory for storing a respective portion of the data set so that at any time the entire data set is stored in the random access memories of the stream server computers; and

a stream server controller linked to the stream server computers and programmed for (a) maintaining the respective portion of the data set in the random access memory of said each stream server computer as a sliding window into the data set by loading new data into the respective portion of the data set in the random access memory of said each stream server computer at approximately a rate at which data are isochronously streamed to the clients for viewing, wherein at any time the entire data set is stored in the random access memories of the stream server computers but the entire data set is not stored in the random access memory of any one of the stream server computers and the respective portion of the data set in said each stream server computer partially overlaps the respective portion of the data set in another one of the stream server computers; and

(b) servicing a request of the client for viewing of the data set beginning at the specified location in the data set by establishing a data link to the client from a selected one of the stream server computers currently having in its random access memory a respective portion of the data set including the specified location in the data set, and transferring video data over the data link from the random access memory of the selected one of the stream server computers to the client.

11. The video file server as claimed in claim 10, further including a storage subsystem for storing said video data set, and wherein the stream server computers are programmed for fetching new data from the storage subsystem for the loading of the new data into the respective portion of the data set in the random access memory of said each stream server computer at approximately the rate at which data are isochronously streamed to the clients for viewing.

12. The video file server as claimed in claim 10, wherein the stream server computers are programmed for transferring new data between the respective portions of the data set in the random access memories of the stream server computers for the loading of the new data into the respective portion of the data set in the random access memory of said each stream server computer at approximately the rate at which data are isochronously streamed to the clients for viewing, and the stream server computers are programmed to transfer the new data to the respective portion of the data set in the random access memory of said each stream server computer from another portion of the data set in the random access memory of another one of the stream server computers.

13. The video file server as claimed in claim 10, wherein the stream server computers are programmed for transferring video data for the entire data set from the random access memory of the selected stream server computer to the client, without reassigning the client to another stream server computer.

14. The video file server as claimed in claim 10, wherein the stream server computers are programmed for transferring video data for the entire data set from the random access memory of said each stream server computer to multiple clients simultaneously.

15. The video file server as claimed in claim 10, wherein the stream server controller is programmed for holding some random access memory of the stream server computers in reserve and is not needed for storing the entire data set in the random access memories of the stream server computers, and when a stream server computer becomes highly loaded by client requests, allocating the reserve memory in another stream server computer to store a duplicate of a respective portion of the data set in the stream server computer that is highly loaded, the reserve memory in said another stream server computer being allocated in response to a client request for isochronous access to the respective portion of the data set in the stream server computer that is highly loaded, said client request for isochronous access to the respective portion of the data set in the stream server computer that is highly loaded being serviced by said stream server computer that is highly loaded by isochronously streaming data from the random access memory of the stream server computer that is highly loaded, the reserve memory being allocated to provide service for possible additional client requests for isochronous access to the respective portion of the data set in the stream server computer that is highly loaded.

16. A method of operating a video file server to provide video-on-demand service to clients in a data network, said video file server having a storage subsystem for storing a video data set, and a plurality of stream server computers linking the data storage subsystem to the data network, each stream server computer having a random access memory for storing a portion of the data set so that the data set is replicated in the random access memory of the stream server computers, wherein the method comprises the steps of:

(a) receiving a request from a client for streaming data from the data set;

(b) checking whether said client is requesting data existing in the random access memory of one of said stream server computers having sufficient resources for streaming the requested data from the random access memory of said one of said stream server computers to said client, and

(i) when said client is requesting data existing in the random access memory of one of said stream server computers having sufficient resources for streaming the requested data from the random access memory of said one of said stream server computers to said client, assigning said one of said stream server computers to handle said request from said client by streaming the requested data from the random access memory of said one of said stream server computers to said client; and

(ii) when said client is requesting data that does not exist in the random access memory of any of the stream server computers having sufficient resources to handle the request, checking whether any of said stream server computers has sufficient random access memory to handle said request from said client by streaming the requested data from said sufficient random access memory to said client, and when any of said stream server computers has sufficient random access memory to handle said request from said client by streaming the requested data from said sufficient random access memory to said client, loading the requested data into said sufficient random access memory, and servicing the request by streaming the requested data from said sufficient random access memory to said client;

wherein said method further includes, upon assigning said one of said stream server computers to handle said request from said client, checking whether said one of said stream server computers has sufficient resources for handling at least one possible additional client request for said data existing in the random access memory of said one of said stream server computers, and when said one of said stream server computers does not have sufficient resources for handling at least one possible additional client request for said data existing in the random access memory of said one of said stream server computers, loading random access memory of another one of said stream server computers with said data existing in the random access memory of said one of said stream computer computers, before receiving said possible additional client request.

17. The method as claimed in claim 16, wherein said one of said stream server computers handles said request from said client by maintaining a sliding window into the data set by loading new data into the portion of the data set in the random access memory of said one of said stream server computers at approximately a rate at which data are delivered to said client.

18. The method as claimed in claim 17, wherein said one of said stream server computers handles said request from said client by fetching new data from the storage subsystem and loading the new data into the portion of the data set in the random access memory of said one of said stream server computers at approximately a rate at which data are delivered to said client.

19. The method as claimed in claim 18, wherein the new data are transferred between the portions of the data set in the random access memory of the stream server computers for the loading of the new data into the portion of the data set in the random access memory of said one of said stream server computers at approximately a rate at which data are delivered to said client.

20. The method as claimed in claim 16, wherein video data for the entire data set are transferred from the random access memory of said on e of said stream server computers to said client, without reassigning said client to another stream server computer, and without the entire data set being stored in the random access memory of said one of said stream server computers.

21. The method as claimed in claim 16, wherein video data for the entire data set are transferred from the random access memory of said one of said stream server computers to multiple clients simultaneously.