Adaptive remote copy in a heterogeneous environment

• US 20050021627A1
• Filed: 09/12/2003
• Published: 01/27/2005
• Est. Priority Date: 01/08/1997
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Oeda, Takashi, Achiwa, Kyosuke, Nakamura, Katsunori, Koide, Takeshi, Nagasawa, Teruo
• Granted Patent: US 7,114,049 B2
• Time in Patent Office: Days
• US Class Current: 709/205
• CPC Class Codes: G06F 11/2038 with a single idle spare processing component
• CPC Class Codes: G06F 11/2058 using more than 2 mirrored copies
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2071 using a plurality of controllers
• CPC Class Codes: G06F 11/2074 Asynchronous techniques
• CPC Class Codes: G06F 11/2082 Data synchronisation

Abstract

A storage apparatus system comprises first and second data storage systems. The first data storage systems can copy an image of data stored therein to the second data storage system without affecting access to storage in the first data storage system. In addition, failover processing is provided between the first and second data storage systems, wherein the second data storage system serves as the failover system.

Claims

1. A storage system comprising:

a first computer system configured to receive storage access requests from one or more user systems and to process the storage access requests;

a first data storage system operative with the first computer system to satisfy received storage requests, the first data storage system comprising a plurality of data volumes including a primary volume and a primary difference volume;

a second computer system;

a second data storage system operative with the second computer system and comprising a plurality of data volumes including a secondary volume and a secondary difference volume;

a first communication path between the first and second computer systems; and

a second communication path between the first data storage system and the second data storage system,

the first data storage system configured to perform steps of storing data received from the first computer system to the primary volume and communicating blocks of data from the primary volume to the second data storage system, and in response to receiving a first command from the first computer system;

selectively storing subsequent data received from the first computer system to the primary difference volume;

communicating blocks of data from the primary volume to the second data storage system; and

upon completing the step of communicating blocks of data, communicating a first signal to the second data storage system,

the second computer system configured to receive a second command from the first computer system and in response to take over receiving and processing of storage access requests whereby the first computer system ceases to process storage access requests,

the second data storage system configured to selectively access first data stored on the first data storage system in order to service a storage access request received by the second computer system and further configured to store the first data in the second data storage system.

2. The storage system of claim 1 wherein the step of selectively storing includes storing the subsequent data on the primary difference volume if a block on the primary volume to which the subsequent data would be written contains data that had not yet been communicated to the second data storage system at a time when the first command was received, and storing the subsequent data on the primary volume if the block on the primary volume had already been communicated to the second data storage system at the time when the first command was received.

3. The storage system of claim 1 wherein the second data storage system is further configured to perform steps of storing data received from the first data storage system to the secondary difference volume, and in response to receiving the first signal, copying data contained in the secondary difference volume to the secondary volume.

4. The storage system of claim 1 further comprising a primary bit map stored in the first data storage system, wherein the steps of communicating blocks of data from the primary volume to the second data storage system is performed based on the primary bit map.

5. The storage system of claim 4 wherein blocks of data that are communicated to the second data storage system after receiving the first command are those blocks of data that had not yet been communicated to the second data storage system prior to receiving the first command.

6. The storage system of claim 1 wherein the first data is data that had not yet been communicated from the first data storage system to the second data storage system at the time the second computer system received the second command.

7. The storage system of claim 1 wherein the second data storage system includes an additional secondary difference volume and in further response to receiving the first signal, storing data that is received from the first data storage system to the additional secondary difference volume.

8. A data storage method comprising:

(a) operating in a first mode, including;

i) receiving and processing storage access requests from one or more user systems;

ii) if one of the storage access requests is a write request of data, then storing the data on a primary volume of a first data storage system;

iii) if one of the storage access requests is a read request, then accessing the primary volume to service the read request;

iv) communicating data stored on the primary volume to a second data storage system; and

v) storing data received from the first data storage system to a secondary difference volume of the second data storage system;

(b) operating in a second mode in response to the first data storage system receiving a first command, the first command being received at a time T, including;

i) selectively storing subsequent data, received after time T, to a primary difference volume of the first data storage system;

ii) communicating certain data on the primary volume to a second data storage system, the certain data being data that had not yet been communicated to the second data storage system at time T;

iii) storing data received from the first data storage system to the secondary difference volume; and

iv) when all of the certain data has been communicated to the second data storage system then copying data from the primary difference volume to the primary volume and copying data from the secondary difference volume to a secondary volume of the second data storage system; and

(c) operating in a third mode, including;

i) receiving and processing storage access requests from the one or more user systems;

ii) if one of the storage access requests is a write request of data, then storing the data to the secondary volume; and

iii) if one of the storage access requests is a read request, then selectively accessing the primary volume to service the read request, and if data is read from the primary volume then copying it to the second data storage system.

9. The method of claim 8 wherein the step of selectively storing includes storing the subsequent data to the primary difference volume if data in a data block of the primary volume to which the subsequent data is to be written had not yet been communicated to the second data storage system at time T, and storing the subsequent data to the primary volume if data in the data block of the primary volume had already been communicated to the second data storage system at time T.

10. The method of claim 8 wherein in the step of operating in a first mode, the steps of receiving and processing are performed by a first host computer, wherein in the step of operating in a third mode, the steps of receiving and processing are performed by a second host computer.

11. The method of claim 8 wherein in the step of operating in a second mode, the certain data is identified by a primary bitmap which indicates which data has been communicated to the second data storage device and which data has not been communicated to the second data storage device.

12. The method of claim 8 wherein in the step of operating in a third mode, the step of selectively accessing the primary volume is based on a bitmap which indicates which data has already been copied from the primary volume and which data has not been copied from the primary volume.

13. A data storage system comprising:

first host means for receiving and processing storage access requests;

first storage means, in communication with the first host means, for storing data;

second host means for receiving and processing storage access requests, wherein only one of the first and second host means is active at any one time to process storage access requests;

second storage means, in communication with the second host means, for storing data;

first communication means for communication between the first host means and the second host means,

second communication means between the first storage means and the second storage means,

the first storage means comprising first controller means for writing data to a first volume in the first storage means and for communicating stored data from the first volume to the second storage means, the stored data being stored on a second volume in the second storage means,

the first controller further for writing data to a first differential volume in the first storage means instead of to the first volume in response to receiving a first command from the first host means,

the first controller further for communicating certain data from the first volume to the second storage means in response to receiving the first command, the certain data being data that had not yet been communicated to the second storage means at the time of receiving the first command, the certain data being stored on the second volume,

the second host means further for taking over the receiving and processing of storage access requests in response to receiving a second command from the first host means, wherein the first host means ceases to process storage access requests,

the second storage means comprising a second controller means, responsive to the second command, for selectively accessing the first volume to retrieve data therefrom in order to service a read request and for storing that data in the second volume.