Method for scheduling I/O transactions for video data storage unit to maintain continuity of number of video streams which is limited by number of I/O transactions

• US 5,721,950 A
• Filed: 09/10/1996
• Issued: 02/24/1998
• Est. Priority Date: 11/17/1992
• Status: Expired due to Fees

• Current Assignee: Starlight Networks, Inc. (Plantronics, Inc.)
• Original Assignee: Starlight Networks, Inc. (Plantronics, Inc.)
• Inventors: Gang, Joseph M. Jr., McFadden, Martin J., Baird, Randall B., Tobagi, Fouad A., Pang, Joseph W. M.
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): Perveen, Rehana
• Application Number:
  US08/711,049
• Time in Patent Office: 532 Days
• Field of Search: 395/826, 395/825, 395/841, 395/800, 395/174, 395/328
• US Class Current: 710/6
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G11B 2220/20 Disc-shaped record carriers
• CPC Class Codes: G11B 27/105 of operating discs
• CPC Class Codes: H04N 21/21 Server components or server architectures
• CPC Class Codes: H04N 21/23 Processing of content or additional data; Elementary server operations; Server middleware
• CPC Class Codes: H04N 7/17336 Handling of requests in head-ends
• CPC Class Codes: H04N 7/24 Systems for the transmission of television signals using pulse code modulation H04N21/00 takes precedence

Abstract

A method for operating a disk storage system, comprising a disk and forming part of a communications network, simultaneously maintains the continuity of a plurality of data streams. Typically, each stream transfers video data to or from the disk storage system. Illustratively, each of the data streams is produced in the network at a rate of W_base bits/sec and consumed by the disk storage system or produced by said disk storage system and consumed in the network at a rate of W_base bits/sec. One I/O transaction is performed for each stream in each of a plurality of I/O cycles of duration S/W_base, wherein in each I/O transaction a segment of S bits is retrieved from or stored in the disk. The number of streams whose continuity can be maintained in this manner is limited by the number of I/O'"'"'s which can be performed in a cycle of duration S/W_base. More generally, when a stream has a bit rate (A/B)W_base bits/sec where A and B are integers chosen independently for each stream, then for this stream A I/O transactions are performed in B cycles of duration S/W_base. If the number of disks is N_d,N_d ≧1, then the I/O cycles have a duration N_d S/W_base and then A I/O transactions are performed in each disk for each stream in B I/O cycles.

Claims

1. A method for scheduling I/O transactions for a data storage unit which stores data for a plurality of full motion video streams, comprising the steps of:

maintaining simultaneously the continuity of all of said full motion video streams by performing one I/O transaction in said storage unit for each stream in each of a plurality of successive I/O cycles of a predetermined duration T_play, wherein the number of streams whose continuity can be simultaneously maintained is limited by the number of I/O transactions which can be performed in said storage system in the period of duration T_play,

in each of said I/O transactions a segment of S bits is retrieved from said storage unit or written into said storage unit,

each of said streams having a bit rate of W_base bits/sec,

said duration of each I/O cycle being T_play =S/W_base,

the duration of each I/O transaction being shorter than T_play,

each of said segments retrieved from said storage unit in an I/O transaction being consumed in a consumption cycle of a stream of duration S/W_base which begins after the I/O transaction,

each of said segments written into said storage unit in an I/O transaction being produced in a production cycle of a stream of duration S/W_base which ends prior to the I/O transaction.

2. The method of claim 1 wherein said storage system is located in a network and each of said streams is either produced or consumed in said network.

3. The method of claim 1 wherein said I/O transactions for each stream are performed in a predetermined order in each I/O cycle.

4. The method of claim 1 wherein the order in which said I/O transactions are performed for each of said streams in each of said I/O cycles is determined individually for each I/O cycle.

5. The method of claim 4 wherein production and consumption cycles of said streams are aligned with said I/O cycles and further comprising the steps of:

during the i^th cycle of duration T_play, storing in said storage system segments of S bits belonging to particular streams and produced by said network in the (i-1)^th cycle and retrieving from said storage system segments of S bits belonging to particular streams and consumed by said network in the (i+1)^th cycle.

6. The method of claim 1 wherein said storage system comprises a disk, said disk is organized into bins of size S bits and segments are allocated to bins randomly.

7. The method of claim 1 wherein said storage system comprises a disk and wherein segments belonging to often-accessed files are located in outer zones in said disk and segments belonging to rarely-accessed files are located in inner zones of said disk.

8. The method of claim 1 wherein said storage system comprises a disk and wherein segments are stored in the outer zones of said disk when said disk is not full.

9. The method of claim 1 wherein said storage system comprise a disk and wherein segments belonging to particular files are stored contiguously on said disk.

10. The method of claim 2 wherein said network is a local area network.

11. The method of claim 1 wherein said streams contain video data.

12. The method of claim 1 wherein said streams include audio data.

13. The method of claim 1 wherein said streams have a bit rate of (A/B) W_base bits/see, where A and B are integers chosen separately for each stream, wherein said storage system comprises N_d,N_d ≧

1, storage units, each I/O cycle has a duration of N_d T_play and for each stream, A I/O transactions take place for each storage unit in B I/O cycles.