STORAGE SYSTEM AND ITS CONTROL METHOD

• US 20110191554A1
• Filed: 07/17/2009
• Published: 08/04/2011
• Est. Priority Date: 07/17/2009
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Noborikawa, Yoshiyuki, Nagata, Koji, Sakai, Kosuke
• Granted Patent: US 8,352,681 B2
• Time in Patent Office: Days
• US Class Current: 711/162
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

Proposed are a highly reliable storage system and its control method capable of accelerating the processing speed of the copy processing seen from the host device.

With the storage system and its control method which stores a command issued from a host device in a command queue and executes the command stored in the command queue in the order that the command was stored in command queue, a copy queue is set for temporarily retaining a copy command among the commands issued from the host device in the memory, the copy command among the commands is moved from the host device stored in the command queue to the copy queue and an execution completion reply of copy processing according to the command is sent to the host device as a sender of the command, and the copy command that was moved to the copy queue is executed in the background in the order that the copy command was stored in the copy queue.

Claims

1. A storage system, comprising:

a memory set with a command queue for temporarily retaining a command from a host device; and

a control unit for storing the command issued from the host device in the command queue, and executing the command stored in the command queue in the order that the command was stored in the command queue,

wherein the control unit sets a copy queue for temporarily retaining a copy command among the commands issued from the host device in the memory,

moves the copy command among the commands from the host device stored in the command queue to the copy queue and sends an execution completion reply of copy processing according to the command to the host device as a sender of the command, and

executes the copy command that was moved to the copy queue in the background in the order that the copy command was stored in the copy queue.

2. The storage system according to claim 1,

wherein, upon executing a read command or a write command stored in the command queue, the control unit determines whether a copy command designating an area which partially or entirely overlaps with a read area or a write area designated in the read command or the write command as a copy source or a copy destination is stored in the copy queue, and

executes read processing or write processing according to the determination result.

3. The storage system according to claim 2, further comprising a hash table including a plurality of slots,

wherein, upon receiving the copy command from the host device, the control unit associates the slot with a copy source area or a copy destination area of the copy command according to a starting address of the copy source area or the copy destination area in the hash table, and

uses the hash table to determine whether a copy command designating an area which partially or entirely overlaps with a read area or a write area designated in the read command or the write command as a copy source or a copy destination is stored in the copy queue.

4. The storage system according to claim 2,

wherein, upon executing a read command stored in the command queue, if a copy command designating an area which partially or entirely overlaps with a read area designated in the read command as a copy destination is stored in the copy queue and copy to [the] area in which the read area and the copy destination area of the copy command overlap has not yet been executed, the control unit copies data from a copy source area of the copy command to the overlapping area and thereafter reads data.

5. The storage system according to claim 2,

wherein, upon executing a write command stored in the command queue, if a copy command designating an area which partially or entirely overlaps with a write area designated in the write command as a copy source is stored in the copy queue and copy to [the] area in which the write area and the copy source area of the copy command overlap has not yet been executed, the control unit saves data stored in the overlapping area and thereafter writes write data.

6. The storage system according to claim 2,

wherein, upon executing a write command stored in the command queue, if a copy command designating an area which partially or entirely overlaps with a write area designated in the write command as a copy destination is stored in the copy queue and copy to [the] area in which the write area and the copy destination area of the copy command overlap has not yet been executed, the control unit copies data stored in a copy source area of the copy command to the overlapping area and thereafter writes write data.

7. A control method of a storage system which stores a command issued from a host device in a command queue and executes the command stored in the command queue in the order that the command was stored in command queue, comprising:

a first step of setting a copy queue for temporarily retaining a copy command among the commands issued from the host device in the memory;

a second step of moving the copy command among the commands from the host device stored in the command queue to the copy queue and sending an execution completion reply of copy processing according to the command to the host device as a sender of the command; and

a third step of executing the copy command that was moved to the copy queue in the background in the order that the copy command was stored in the copy queue.

8. The control method of a storage system according to claim 7, further comprising:

a determination step of determining, upon executing a read command or a write command stored in the command queue, whether a copy command designating an area which partially or entirely overlaps with a read area or a write area designated in the read command or the write command as a copy source or a copy destination is stored in the copy queue; and

a processing execution step of executing read processing or write processing according to the determination result.

9. The control method of a storage system according to claim 8,

wherein the storage system comprises a hash table including a plurality of slots,

wherein, at the determination step, upon receiving the copy command from the host device, the slot is associated with a copy source area or a copy destination area of the copy command according to a starting address of the copy source area or the copy destination area in the hash table, and

the hash table is used to determine whether a copy command designating an area which partially or entirely overlaps with a read area or a write area designated in the read command or the write command as a copy source or a copy destination is stored in the copy queue.

10. The control method of a storage system according to claim 8,

wherein, at the processing execution step, upon executing a read command stored in the command queue, if a copy command designating an area which partially or entirely overlaps with a read area designated in the read command as a copy destination is stored in the copy queue and copy to [the] area in which the read area and the copy destination area of the copy command overlap has not yet been executed, data is copied from a copy source area of the copy command to the overlapping area and data is thereafter read.

11. The control method of a storage system according to claim 8,

wherein, at the processing execution step,

upon executing a write command stored in the command queue, if a copy command designating an area which partially or entirely overlaps with a write area designated in the write command as a copy source is stored in the copy queue and copy to [the] area in which the write area and the copy source area of the copy command overlap has not yet been executed, data stored in the overlapping area is saved and write data is thereafter written.

12. The control method of a storage system according to claim 8,

wherein, at the processing execution step,

upon executing a write command stored in the command queue, if a copy command designating an area which partially or entirely overlaps with a write area designated in the write command as a copy destination is stored in the copy queue and copy to [the] area in which the write area and the copy destination area of the copy command overlap has not yet been executed, data stored in a copy source area of the copy command is copied to the overlapping area and write data is thereafter written.