Disk array system using detachable memory medium

• US 5,564,033 A
• Filed: 06/29/1994
• Issued: 10/08/1996
• Est. Priority Date: 06/29/1993
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Satake, Shozo, Kawashita, Asayoshi, Takekuma, Toshitsugu
• Primary Examiner(s): Bowler, Alyssa H.
• Assistant Examiner(s): ODEDRA, DHIREN
• Application Number:
  US08/267,385
• Time in Patent Office: 832 Days
• Field of Search: 395/825, 395/829, 395/830, 395/833, 395/837, 395/404, 395/405, 395/442, 395/444, 395/497.01, 395/182.03, 395/182.04, 395/182.05, 395/474, 395/479, 395/481, 365/189.04, 365/230.01
• US Class Current: 711/115
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems

Abstract

An external memory unit for a data processing system has a plurality of detachable memory media. Data is written in parallel to the memory media. Since the positions of the memory media can be switched, reference information is written in each of the media during an initialization process. Once initialized, the data can be read from and written to the memory media regardless of their current and former positions in the external memory unit. The reference information has sequence information indicating the position of a memory medium in a sequence when data is first written to a group of media as part of an operation that subdivides data and writes the subunits to the group. The name of the group is also included in the reference information. When a subsequent read or write operation is requested, the group information is used to determine if all of the media required for executing the request are present in the external memory unit, and if so, the operation is executed.

Claims

1. A peripheral memory unit for use with a data processing system, comprising:

said memory unit having a plurality of detachable memory media for storage of data;

means for dividing units of data to be stored into a series of divided subunits of data;

means for initializing each of said memory media including storing reference information in each of said memory media to be used for restoring said divided subunits of data into said units of data during a read operation;

means for writing in parallel said subunits of data in accordance with said reference information among said plurality of memory media;

means for reading said reference information stored in said memory media;

means for reading in parallel said divided subunits of data in accordance with said reference information read from said plurality of memory media; and

means for receiving and restoring said divided subunits of data read by said divided data reading means and for outputting said divided subunits as said units of data;

wherein said writing means writes said subunit of data in a sequence and;

wherein said means for reading said reference information in response to receiving a read/write instruction first reads said group information from each of said memory media to determine if all said memory media in said memory unit are part of said predetermined group of said memory media required for executing the read/write instruction, and then reads said partial sequence data when it is determined that all of said memory media required for executing the read/write instruction are present;

wherein said means for reading said reference information includes means for determining an access sequence from said partial sequence data; and

further wherein said means for reading said subdivided data reads said subunits from said memory media in accordance with said access sequence.

2. A memory unit according to claim 1, wherein said initializing means stores group information identifying a predetermined group of said plurality of memory media to which data is to be written to or read from as said reference information.

3. A memory unit according to claim 2, wherein said means for reading said reference information, in response to receiving a read or write instruction, first reads said group information from each of said memory media to determine if all of said memory media in said memory unit are part of said predetermined group of said memory media required for executing the read or write instruction, and then outputs a read or write instruction interruption signal if any of the memory media in said memory unit is not within said predetermined group.

4. A memory unit according to claim 2, wherein said writing means writes said divided subunits of data to said predetermined group of memory media in a sequence and said initializing means writes partial sequence data in each of said memory media identifying a place in said sequence that each said memory media has been assigned by said writing means as said reference information.

5. A memory unit according to claim 4, wherein said means for reading said reference information, in response to a read or write instruction, reads said group information from each of said memory media to determine if all of said memory media in said memory unit are part of said predetermined group of said memory media, and also reads said partial sequence data for determining an access sequence used by said reading means for reading said subunits of data to provide said subunits to said restoring means in said sequence.

6. A memory unit according to claim 1, wherein said writing means writes said subunits of data among said plurality of memory media in a sequence and said initializing means writes partial sequence data in each of said memory media identifying a place in said sequence that each said memory media has been assigned by said writing means, as said reference information.

7. A peripheral memory unit for use with a data processing system, comprising:

said memory unit having a central processing unit and a plurality of detachable memory media for storage of data;

means for dividing units of data to be stored into a series of divided subunits of data;

means for initializing each of said memory media including generating and storing reference information including group information identifying a predetermined group of said plurality of memory media to which data is to be written to or read from each of said memory media to be used for reading and restoring said divided subunits of data;

means for writing in parallel said subunits of data in a sequence among said group of memory media;

means for reading said reference information and for reading in parallel said divided subunits of data from said group of memory media in accordance with said reference information and for restoring said divided subunits into said units of data;

wherein said means for reading said reference information, in response to receiving a read or write instruction, determines if all of said memory media in said memory unit are part of said predetermined group of said memory media required for executing the read or write instruction; and

wherein said central processing unit suspends execution of said read or write instruction when one of said memory media is determined to not be part of said predetermined group;

wherein said means for reading said reference information reads said partial sequence data and determines an access sequence from said partial sequence data; and

further wherein said means for reading said subunits of divided data reads said subunits from said memory media in accordance with said access sequence.

8. A memory unit according to claim 7, wherein said initializing means writes partial sequence data in each of said memory media of said predetermined group identifying a place in said sequence that each said memory media has been assigned by said writing means.

9. A memory unit according to claim 7, wherein said means for reading said reference information outputs an error notice to a user if any of the memory media in said memory unit is determined to be not within said predetermined group.

10. A memory unit according to claim 7, wherein, in response to said central processing unit executing a write instruction, said writing means writes addresses of the written data in said memory media.

11. A memory unit according to claim 8, wherein, in response to said central processing unit executing a write instruction, said writing means writes divided data having one of odd and even addresses alternately to respective one of two of said memory media as said predetermined group of said memory media and writes addresses of the written data respectively in said two memory media.

12. A memory unit according to claim 11, wherein, in response to a read instruction, said reference information reading means reads said odd and even addresses and said reading means reads said divided subunits of data alternately from the respective ones of said two memory media in accordance with said odd and even addresses.

13. A memory unit according to claim 12, wherein said read and said write instructions are performed in parallel.

14. A memory unit according to claim 7, further comprising an internal fixed storage device wherein, in response to said central processing unit executing a write instruction, said writing means writes addresses of the divided subunits of data written in said memory media to said storage device.

15. A memory unit according to claim 8, further comprising an internal fixed storage device wherein, in response to said central processing unit executing a write instruction, said writing means writes said divided subunits of data having one of odd and even addresses alternately to respective one of two of said memory media as said predetermined group of said memory media and writes addresses of the written data in said storage device.

16. A memory unit according to claim 15, wherein, in response to a read instruction, said reference information reading means reads said odd and even addresses stored in said storage device and said reading means alternately reads from respective ones of said two memory media in accordance with said odd and even addresses.

17. A peripheral memory unit for use with a data processing system, comprising:

said memory unit having a plurality of means for receiving respective detachable memory media for storage of data;

means for dividing units of data to be stored into a series of divided subunits of data;

means for initializing each of said memory media including generating and storing reference information including group information identifying a predetermined group of said plurality of memory media to which data is to be written to or read from reference information in each of said memory media to be used for restoring said divided subunits of data into said units of data during a read operation;

means for writing in parallel said subunits of data in a sequence to each of said memory media received in said receiving;

means, in response to receiving a read or write instruction, for reading said reference information of each of said respective memory media received in said plurality of receiving means to determine if all of said memory media in said predetermined group are received in said corresponding receiving means; and

said central processing unit suspending execution of said read/write instruction when at least one of said memory media of said predetermined-group is determined to not be in a corresponding one of said receiving means;

wherein said means for reading said reference information, in response to receiving a read or write instruction, reads said group information from each of said memory media to determine if all of said memory media in said memory unit are part of said predetermined group of said memory media required for executing the read/write instruction, and also reads said partial sequence data for determining an access sequence used by said reading means for reading said subunits of data in said sequence in which said subunits were written by said writing means.

18. A memory unit according to claim 17, wherein said initializing means stores data identifying all of said memory media within said predetermined group in each of said memory media as part of said reference information.