Modular high-capacity solid-state mass data storage device for video servers

Abstract: A modular solid-state mass data storage device providing high-density, high-capacity storage of numerous full-length movies for video server applications. The mass data storage device employs a modular pipeline architecture in which a distributed array of controller/memory modules is arranged in parallel controller/memory channels on one or more controller/memory cards. The modular pipeline architecture allows the number of controller/memory modules in each channel to be easily configured to accommodate any required storage size and the number of controller/memory channels to be configured to accommodate any required storage size and transfer rate, without increasing latency time. The modular pipeline architecture also greatly simplifies the complexity of the memory controllers, and high-density packaging of the controller/memory modules provides compact storage for large amounts of data. An asynchronous transfer mode (ATM) switch allows multiple viewers to access the movies stored in the mass data storage device with independent VCR-like control of the movie being watched.

Description: This invention relates generally to mass data storage devices and, more particularly, to solid-state random access memory (RAM) mass data storage devices for video server applications. Video-on-demand will provide home television viewers the ability to watch movies of their choice at any time of the day in the comfort of their homes. Centrally-located video servers will store current popular movies and allow thousands of viewers simultaneous access to these movies at any one time. Less popular current movies or older movies will be downloaded to the video server upon demand. Home television sets will be connected to the video servers by phone lines, using either copper or fiber optic cables. Each viewer will have independent VCR-like (Video Cassette Recorder) control over the movie being watched. Each video server will include some type of mass data storage device for storing the movies. Hard disk or optical disk storage devices could be used, but the latency times are too long for independent VCR-like control of numerous movies by thousands of viewers. Magnetic tape does not allow for multiple accesses of a movie at different times or independent VCR control of a movie by different viewers. Therefore, the mass data storage device will likely be a solid-state RAM storage device. However, solid-state RAM mass data storage devices still do not provide the high densities and large memory capacities that are required by video servers, even though refinements in semiconductor fabrication techniques have reduced the unit cost and increased the unit density of solid-state RAM memory devices. Accordingly, there has been a need for a high-capacity solid-state mass data storage device for video server applications. A typical example of video-on-demand system is disclosed in US-A-5133079. Here, movies are stored in compression digital form in a Central Distribution Library. The detailed structure of the Library is not specified. Examples given are CD-ROM, WORM, hard disk and solid state memory. EP-A-0402135 discloses a picture reproducing apparatus in which one or two frames of video data are stored in a memory and retrieved when selected for output to a video monitor. The apparatus operates in conjunction with a video tape recorder (VTR) or similar device and is used to provide a still video picture when the VTR is engaged in a rewind or fast-forward operation. Thus, the memory of such a device only needs to store one or two frames of video data. One example of a suitable memory is illustrated which comprises an array of modules with a single controller providing random access to the multiple memory modules. The present invention provides a modular solid-state mass data storage device providing high-density, high-capacity storage of one or more movies for video servers, characterised by: a distributed array of controller-and-memory modules arranged in parallel controller-and-memory channels on one or more memory cards, the distributed array having a modular pipeline architecture in which each controller-and-memory channel has multiple controller-and-memory modules connected in a serial chain by address, data and control buses; and an asynchronous transfer mode (ATM) switch for simultaneous access by multiple viewers of the one or more movies stored in the controller-and-memory modules; wherein the address, data and control buses connecting the controller-and-memory modules in each channel include first and second buses which extend from a data format module, the first bus also connecting an output of the last controller-and-memory module in each channel back to an input of the data format module. SUMMARY OF THE INVENTION The present invention resides in a modular solid-state mass data storage device providing high-density, high-capacity storage of numerous full-length movies for video server applications. The modular pipeline architecture allows the number of controller-and-memory modules, hereinafter "controller/memory modules" in each channel to be easily configured to accommodate any required storage size and the number of controller-and-memory channels hereinafter "controller/memory channels" to be configured to accommodate any required storage size and transfer rate, without increasing latency time. The modular pipeline architecture also greatly simplifies the complexity of the memory controllers, and high-density packaging of the controller/memory modules provides compact storage for large amounts of data. An asynchronous transfer mode (ATM) switch allows multiple viewers to access the movies stored in the mass data storage device with independent VCR-like control of the movie being watched. In a preferred embodiment of the present invention, each controller/memory card includes eight parallel controller/memory channels. Each controller/memory module includes an 8x4 array of 4MBit DRAM chips for a total memory capacity per module of 16 MBytes. Each set of eight parallel controller/memory modules is packaged in two high-density SIMM modules, for a total memory capacity per SIMM module of 64 MBytes and a data transfer rate of 200 MBytes/sec. Each controller/memory card includes twenty SIMM modules for a total memory capacity of 1.0 GByte with error correction. Each controller/memory card can store one full-length movie with compression. Sixty four controller/memory cards provide a total memory capacity of 64 GBytes and can store sixty four full-length movies. It will be appreciated from the foregoing that the present invention represents a significant advance in the field of solid-state mass data storage devices for video server applications. Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a modular, high-capacity solid-state mass data storage device for video server applications in accordance with the present invention; and Figure 2 is a block diagram of a controller/ memory module in the mass data storage device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings for purposes of illustration, the present invention is embodied in a modular solid-state mass data storage device providing high-density, high-capacity storage of numerous full-length movies for video server applications. The mass data storage device employs a modular pipeline architecture in which a distributed array of controller/memory modules is arranged in parallel controller/memory channels on one or more controller/memory cards. The modular pipeline architecture allows the number of controller/memory modules in each channel to be easily configured to accommodate any required storage size and the number of controller/memory channels to be configured to accommodate any required storage size and transfer rate, without increasing latency time. The modular pipeline architecture also greatly simplifies the complexity of the memory controllers, and high-density packaging of the controller/memory modules provides compact storage for large amounts of data. An asynchronous transfer mode (ATM) switch allows multiple viewers to access the movies stored in the mass data storage device with independent VCR-like control of the movie being watched. As illustrated in Figure 1, the mass data storage device of the present invention includes one or more controller/memory cards 10 which plug into a backplane through a backplane interface 12. An asynchronous mode transfer mode switch 14 allows multiple viewers to access the movies stored in the controller/memory cards 10. Each controller/memory card 10 includes a distributed array of controller/memory modules 16 which are arranged in parallel controller/memory channels. In each channel, the controller/memory modules 16 are connected to first and second buses 18, 20 which extend from a data format module 22. The first bus 18 also extends from the last controller/memory module 16 in each channel back to the data format module 22. The data format module 22 provides data formatting, synchronization and error correction for the data stored in the modules 16. The modular pipeline architecture of the controller/memory channels allows the number of controller/memory modules 16 in each channel to be easily configured to accommodate any required storage size and the number of controller/memory channels to be configured to accommodate any required storage size and transfer rate, without increasing latency time. As illustrated in Figure 2, each controller/memory module 16 includes a memory controller 24 and an array of solid-state dynamic random access memory (DRAM) chips 26. The memory controller 24, which can be greatly simplified because of the pipeline architecture of the present invention, performs all of the basic control functions necessary for accessing the DRAM chips 26. These functions include controlling and addressing the DRAM chips for read/write operations and refreshing the DRAM chips. Each DRAM chip 26 is connected to the memory controller 24 and each memory controller 24 is connected to the other memory controllers in the same channel by the first and second buses 18, 20. The first bus 18 includes a read data bus and the second bus 20 includes a read address bus 28, a write address bus 30, a write data bus 32 and a control bus 34. The read and write buses use a pipeline architecture for both data and address transfers. For the write operation, the write addresses on the write address bus 30 and the data on the write data bus 32 are clocked through the memory controllers 24 in a particular channel until an address matches the write location. The data is then written into that location in the DRAM chip. For the read operation, the read addresses on the read address bus 28 are clocked through the memory controllers 24 in a particular channel until an address matches the read location. The data is retrieved and then clocked on through the remaining memory controllers 24 in that channel on the read data bus 18 back to the data format module 22. In a preferred embodiment of the present invention, each controller/memory card 10 includes eight parallel controller/memory channels. Each controller/memory module 16 includes an 8x4 array of 4MBit DRAM chips 26 for a total memory capacity per module of 16 MBytes. Each set of eight parallel controller/memory modules 16 is packaged in two high-density SIMM modules 36, for a total memory capacity per SIMM module of 64 MBytes and a data transfer rate of 200 MBytes/sec. Each controller/memory card 10 includes twenty SIMM modules 36 for a total memory capacity of 1.0 GByte with error correction. Each controller/memory card 10 can store one full-length movie with compression. Sixty four controller/memory cards 10 provide a total memory capacity of 64 GBytes and can store sixty four full-length movies. Each controller/memory board 10 can simultaneously serve over 1000 viewers, with each viewer having total VCR-like control of the movie. Using a dual I/O port of 200 MBytes/sec, an overhead of 48 Bytes/block access, a user line rate of 1.55 MBit/sec, and a block size greater than 100 KBytes, the number of simultaneous accesses is: (I/O Rate x Block Size)/[Line Rate x (Block Size + Overhead)], which is (1600 MBit/ sec. x 100 KBytes)/[1.55 MBit/sec x (100 KBytes + 48 Bytes)] or 1031. Therefore, with a block size of 100 KByte, up to 1031 viewers can have simultaneous access to each movie. Fifteen accesses can be stacked up at a time. The read and write buses are eight bit buses which are demultiplexed at a ratio of 1:4 and multiplexed at a ratio of 4:1 to reduce system interconnects and memory controller input/output. The controller/memory modules 16 are completely synchronous with all read and write data transfers and the read and write addresses are synchronously clocked for robust timing. Latency time to any address is less than 10 microseconds. Less popular current films or older movies will be stored on magnetic tape, hard disk or optical disk and downloaded on demand. Magnetic tape systems have data transfer rates of 20 MBytes/sec and hard disks have data transfer rates of 30 MBytes/sec. At 20 MBytes/sec, a 1 GByte compressed movie can be downloaded in 50 seconds. A typical video server system will require a workstation and an interface for controlling the mass data storage device. From the foregoing, it will be appreciated that the present invention represents a significant advance in the field of solid-state mass data storage devices for video server applications.

Claims: A modular solid-state mass data storage device providing high-density, high-capacity storage of one or more movies for video servers, characterised by: a distributed array of controller-and-memory modules (16) arranged in parallel controller-and-memory channels on one or more memory cards (10), the distributed array having a modular pipeline architecture in which each controller-and-memory channel has multiple controller-and-memory modules connected in a serial chain by address(28, 30), data (18,32) and control (34) buses; and an asynchronous transfer mode (ATM) switch (14) for simultaneous access by multiple viewers of the one or more movies stored in the controller-and-memory modules; wherein the address, data and control buses connecting the controller-and-memory modules in each channel include first and second buses (18, 20) which extend from a data format module (22), the first bus also connecting an output of the last controller-and-memory module in each channel back to an input of the data format module. The mass data storage device as set forth in claim 1, wherein the data format module provides data formatting, synchronization and error correction for one or more movies stored in the controller-and-memory modules. The mass data storage device as set forth in claim 1, wherein each controller-and-memory module includes an array of dynamic random access memory (DRAM) chips (26) and a memory controller (24) for performing control functions with respect to the array of DRAM chips (26). The mass data storage device as set forth in claim 3, wherein each DRAM chip (26) in a controller-and-memory module (16) is connected to the memory controller (24) for the same controller-and-memory module (16), and each memory controller (24) is connected to the other memory controllers in the same channel by the first and second buses (18, 20). The mass data storage device as set forth in claim 4, wherein the first bus (18) includes a read data bus and the second bus (20) includes a read address bus (28), a write address bus(30), a write data bus (32) and a control bus (34). The mass data storage device as set forth in claim 1, wherein each memory card (10) in the mass data storage device includes eight controller/memory channels, each controller-and-memory module (16) has a memory capacity of 16 megabytes (MBytes), and each memory card has a total memory capacity of over 1 gigabyte (GByte). The mass data storage device as set forth in claim 6, wherein every eight parallel controller-and-memory modules (16) are packaged in a single in-line memory module (SIMM).

Inventors: BRANDIS DIRK KURT, ENYEDY ARTHUR GUSTAV, STOCKTON GRANT JOSEPH, UPTON ERIC LAWRENCE, YOKOTE TIMOTHY ALAN, BRANDIS, DIRK KURT, ENYEDY, ARTHUR GUSTAV, STOCKTON, GRANT JOSEPH, UPTON, ERIC LAWRENCE, YOKOTE, TIMOTHY ALAN
Applicants: TRW INC, TRW INC.
Application year: 1993
Main classification: H04N7
IPC codes: H04L29, G11C5, H04N5, H04N7, G06F12