Redundant storage with mirroring by logical volume with diverse reading process

• US 5,987,566 A
• Filed: 10/06/1998
• Issued: 11/16/1999
• Est. Priority Date: 05/24/1996
• Status: Expired due to Term

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Vishlitzky, Natan, Ofek, Yuval, Bachmat, Eitan
• Primary Examiner(s): BRAGDON, REGINALD GLENWOOD
• Application Number:
  US09/167,161
• Time in Patent Office: 406 Days
• Field of Search: 711/114, 711/162, 395/182.04
• US Class Current: 711/114
• CPC Class Codes: G06F 11/2061 combined with de-clustering of data
• CPC Class Codes: G06F 11/2071 using a plurality of controllers
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2212/312 In storage controller

Abstract

A mirrored memory for a data processing system. The memory system includes two device controllers and related disk drives for storing the mirrored data. Each of the disk drives is divided into logical volumes. Each device controller contains a plurality of reading processes and a correspondence table that establishes the reading process to be used in retrieving data from the corresponding disk drive. Each disk controller responds to a read command that identifies the logical volume by using the correspondence table to select the appropriate reading process and by transferring data from appropriate physical storage device containing the designated logical volume.

Claims

1. A mirrored memory system for retrieving data in response to a read command comprising:

(A) at least a pair of mirroring physical storage devices for storing mirrored copies of related data organized as at least one logical volume, each read command designating a logical volume from which data is to be retrieved,

(B) a reading process module with at least one reading process by which data can be transferred in response to a read command,

(C) a correspondency that assigns to each logical volume the reading process by which data is to be read from said mirroring physical storage devices storing each logical volume, and

(D) a data transfer control module operable in response to said correspondency and said reading process module and connected to said mirroring physical storage devices, said control module responding to a logical volume identification in a read command and the assignment from said correspondency by enabling the transfer of data from one of said mirroring physical storage devices containing the identified logical volume according to the assigned reading process.

2. A memory system as recited in claim 1 wherein the logical volume consists of a set of contiguous tracks on each of said mirroring physical storage devices, said reading process module establishes a reading operation for retrieving data in the logical volume from one of said mirroring physical storage devices and said correspondency assigns the reading process to only one of said mirroring physical storage devices whereby all data from the logical volume is retrieved from the one of said mirroring physical storage devices.

3. A memory system as recited in claim 1 wherein said reading process module establishes complementary reading operations for different portions of the logical volume and said correspondency assigns complementary reading processes to each mirroring physical storage device that stores the logical volume whereby data from a logical volume is retrieved from two of said mirroring physical storage devices.

4. A memory system as recited in claim 3 additionally comprising a table in said correspondency for each mirroring physical storage device that establishes a relationship between the logical volume and one of the complementary reading operations.

5. A memory system as recited in claim 1 wherein said data transfer control module includes a data transfer controller for each of said physical storage devices, said reading process module includes reading process identifications in each of said data transfer controllers and said correspondency includes in each of said data transfer controllers a correspondency table that defines for the logical volume the reading process assigned to the mirrored physical storage devices.

6. A memory system as recited in claim 5 additionally comprising a module that transfers entries to said correspondency tables.

7. A method for transferring in response to a read command, data from one of mirroring physical storage devices comprising the steps of:

(A) storing on the mirrored physical storage devices redundant copies of related data in a logical volume, each read command designating a logical volume from which data is to be retrieved,

(B) defining at least one reading process by which data can be transferred in response to a read command,

(C) assigning in a correspondency a reading process by which data in a logical volume is to be transferred from the mirroring physical storage devices storing the logical volume, and

(D) determining, in response to the logical volume identified in a read command and the reading process identified by said correspondency assignment, the process by which the data will be transferred from the mirroring physical storage devices containing the logical volume.

8. A method as recited in claim 7 wherein the logical volume consists of a set of contiguous tracks on each mirroring physical storage device and one of the at least one reading processes establishes a reading operation for retrieving data for the logical volume from a designated one of the mirroring physical storage devices, said correspondency assignment step establishing which of the mirroring physical storage devices is to provide the data and said determination step enabling data transfers from the designated mirroring physical storage device in response to a read command identifying the logical volume.

9. A method as recited in claim 7 wherein said reading process definition step establishes complementary reading operations for different portions of the logical volume and said correspondency assignment step establishes complementary reading processes to each mirroring physical storage device that stores the logical volume whereby data from a logical volume is retrieved from at least two of the mirroring physical storage devices.

10. A method as recited in claim 9 additionally comprising a step of establishing in said correspondency assignment for each mirroring physical storage device a relationship between the logical volume contained therein and one of the complementary reading operations.

11. A method as recited in claim 7 wherein each of the mirroring physical storage devices connects to a device controller and wherein each device controller stores the reading processes and the correspondency assignments relevant thereto and performs said determining step to determine, in response to the selected reading process identified in the correspondency assignment, the operation of that device controller in response to a read command for data in the logical volume.

12. A method as recited in claim 11 additionally comprising a step of transferring entries to the correspondency assignments in each of the device controllers.

13. A method as recited in claim 12 additionally comprising a step of monitoring the performance of each device controller, one device controller performing a read operation when the operating status of the device controller assigned by the corresponding indicates its inability to perform.