Remote copy system

• US 20060085609A1
• Filed: 12/17/2004
• Published: 04/20/2006
• Est. Priority Date: 10/19/2004
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Ninose, Kenta, Arakawa, Hiroshi, Hirakawa, Yusuke, Asaka, Yoshihiro, Iwamura, Takashige
• Granted Patent: US 7,590,809 B2
• Time in Patent Office: Days
• US Class Current: 711/162
• CPC Class Codes: G06F 11/2058 using more than 2 mirrored copies
• CPC Class Codes: G06F 11/2066 Optimisation of the communication load
• CPC Class Codes: G06F 11/2069 Management of state, configuration or failover
• 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

To provide a computer system constituting a multitarget array and utilizing a remote copy technique for backing up data, in which when a failure occurs in a primary site, a new pair is formed between remaining two secondary sites without copying all data. A first secondary site is associated with the primary site by synchronous remote copy. A second secondary site is associated with the primary site by asynchronous remote copy. A storage system of the first secondary site includes a difference bitmap indicating an area to which data has been written from a host computer. When a failure occurs in a host computer of the primary site, only data of an area indicated by the difference bitmap is transferred to a storage system of the second secondary site.

Claims

1. A computer system, comprising:

a first storage system that is coupled to a first host computer;

a second storage system that is coupled to a second host computer and the first storage system; and

a third storage system that is coupled to the first storage system and the second storage system, wherein;

the first storage system stores data sent from the first host computer,

transfers the data sent from the first host computer to the second storage system by synchronous remote copy, and

transfers the data sent from the first host computer to the third storage system by asynchronous remote copy; and

the second storage system

comprises a first difference bitmap,

updates a bit of the first difference bitmap corresponding to an area to which the data has been written from the second host computer after data is written from the second host computer to the second storage system, and

transfers the data stored in the area corresponding to the updated bit of the first difference bitmap to the third storage system.

2. The computer system according to claim 1,

wherein before the second storage system transfers the data stored in the area corresponding to the updated bit of the first difference bitmap to the third storage system,

the first storage system stops writing data sent from the first host computer,

the second storage system stops transferring data between the first storage system and the second storage system by the synchronous remote copy, and

the first storage system and the third storage system completes transferring data therebetween by the asynchronous remote copy.

3. The computer system according to claim 2,

wherein before stopping transferring the data between the first storage system and the second storage system by the synchronous remote copy, the first storage system stops writing the data sent from the first host computer.

4. The computer system according to claim 1, wherein:

the first storage system comprises a second difference bitmap;

the second storage system stops transferring data between the first storage system and the second storage system by the synchronous remote copy;

the first storage system updates a bit of the second difference bitmap corresponding to an area to which the data has been written from the first host computer after the second storage system stops transferring data between the first storage system and the second storage system by the synchronous remote copy;

the first storage system and the third storage system complete transferring data therebetween by the asynchronous remote copy; and

the second storage system transfers to the third storage system the data stored in the area corresponding to the updated bit of the second difference bitmap.

5. A computer system, comprising:

a first storage system that is coupled to a first host computer;

a second storage system that is coupled to a second host computer and the first storage system; and

a third storage system that is coupled to the first storage system and the second storage system, wherein;

after receiving an instruction to write data from the first host computer, the first storage system

stores an update order identifier for identifying the order of writing the data and the data as a first journal record,

transfers the update order identifier and the data to the second storage system by the synchronous remote copy, and

transfers the first journal record to the third storage system by the asynchronous remote copy;

the second storage system

stores the update order identifier and the data that have been transferred from the first storage system as a second journal record,

stops transferring data between the first storage system and the second storage system by the synchronous remote copy,

stores, after data is written from the second host computer, the written data and an update order identifier that follows the update order identifier that has been transferred from the first storage system as the second journal record, and

transfers the second journal record to the third storage system; and

the third storage system

receives the first journal record that has been transferred from the first storage system,

further receives the second journal record that has been transferred from the second storage system, and

stores the data of the first journal record and the data of the second journal record that have been received, in an order of the update order identifiers.

6. The computer system according to claim 5,

wherein after completing storing the first journal record that has been transferred from the first storage system, the third storage system stores the second journal record that has been transferred from the second storage system.

7. The computer system according to claim 5, wherein:

in a case where a maximum value of the update order identifier of the first journal record stored in the third storage system is equal to or smaller than a maximum value of the update order identifier that has been transferred from the first storage system to the second storage system, the second storage system transfers to the third storage system the second journal record having the update order identifier that is larger than the maximum value of the update order identifier of the first journal record stored in the third storage system; and

in a case where the maximum value of the update order identifier of the first journal record stored in the third storage system is larger than the maximum value of the update order identifier that has been transferred from the first storage system to the second storage system, the second storage system transfers to the third storage system the second journal record having the update order identifier that is larger than the maximum value of the update order identifier that has been transferred from the first storage system to the second storage system.

8. The computer system according to claim 7, wherein:

the second storage system comprises a third difference bitmap;

when the second journal record is erased, the second storage system updates a bit of the third difference bitmap corresponding to an area in which data corresponding to the erased second journal record has been stored;

in one of a case where a minimum value of the update order identifier of the first journal record stored in the third storage system is larger than a maximum value of the update order identifier that has been transferred from the first storage system to the second storage system and a case where a minimum value of the update order identifier of the second journal record stored in the second storage system is larger than a value obtained by adding 1 to the maximum value of the update order identifier of the first journal record stored in the third storage system, the second storage system transfers to the third storage system the data in the area corresponding to the updated bit of the third difference bitmap; and

before storing the data of the second journal record, the third storage system stores the data in the area corresponding to the updated bit of the third difference bitmap that has been transferred from the second storage system.

9. A control method for a computer system,

the computer system comprising:

a first storage system that is coupled to a first host computer;

a second storage system that is coupled to a second host computer and the first storage system, and comprises a first difference bitmap; and

a third storage system that is coupled to the first storage system and the second storage system,

the control method comprising the steps of;

transferring data written from the first host computer to the second storage system by synchronous remote copy;

further transferring the data written from the first host computer to the third storage system by asynchronous remote copy;

writing data sent from the second host computer to the second storage system;

updating a bit of the first difference bitmap corresponding to an area to which the data has been written from the second host computer; and

transferring the data stored in the area corresponding to the updated bit of the first difference bitmap from the second storage system to the third storage system.

10. The control method for a computer system according to claim 9, further comprising the steps of:

stopping writing data sent from the first host computer to the first storage system;

stopping transferring data between the first storage system and the second storage system by the synchronous remote copy; and

completing transferring data between the first storage system and the third storage system by the asynchronous remote copy,

wherein the steps stated above are executed before the step of transferring the data stored in the area corresponding to the updated bit of the first difference bitmap from the second storage system to the third storage system.

11. The control method for a computer system according to claim 10,

wherein the step of stopping writing of the data sent from the first host computer to the first storage system is executed before the step of stopping transferring the data between the first storage system and the second storage system by the synchronous remote copy.

12. The control method for a computer system according to claim 9,

wherein the first storage system comprises a second difference bitmap,

the control method further comprising the steps of:

stopping transferring data between the first storage system and the second storage system by the synchronous remote copy;

updating the bit of the second difference bitmap corresponding to an area to which the data has been written from the first host computer after stopping transferring data between the first storage system and the second storage system by the synchronous remote copy;

completing transferring data between the first storage system and the third storage system by the asynchronous remote copy; and

transferring the data stored in the area corresponding to the updated bit of the second difference bitmap from the second storage system to the third storage system.