# US 2017/0286019 A1 · Storage system and control method therefor

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- Number: US 2017/0286019 A1
- Document ID: US20170286019A1
- Status: Published application
- Kind: A1
- Application number: 15/507,305
- Filed: 2014-11-18
- Published: 2017-10-05
- Earliest claimed: 2014-11-18
- Assignees: Hitachi, Ltd.
- Applicants: Hitachi, Ltd.
- Inventors: Masamitsu TAKAHASHI; Yutaka TAKATA
- Web page: https://patentgrep.com/patent/US20170286019A1

## CPC

- G06F 3/0665: {at area level, e.g. provisioning of virtual or logical volumes}
- G06F 3/06: Digital input from, or digital output to, record carriers {, e.g. RAID, emulated record carriers or networked record carriers}
- G06F 3/065: {Replication mechanisms}
- G06F 12/00: Accessing, addressing or allocating within memory systems or architectures (digital input from, or digital output to record carriers, e.g. to disk storage units, G06F3/06)
- G06F 12/0873: Mapping of cache memory to specific storage devices or parts thereof
- G06F 2212/1024: Latency reduction
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

When the storage system according to the present invention receives a request for writing new data to a first logical volume after having received a first pair creating request, the storage system stores the new data in a cache memory. Then when the storage system subsequently receives a second pair creating request, even if the cache memory still has stored therein the data identical to the data that was stored on the first logical volume at the point in time when the storage system received the first pair formation request, and even if this identical data has not yet been copied to the second logical volume, the storage system omits to copy this identical data to the second logical volume.

## Claims

### Claim 1

A storage system, comprising a processor, a processor memory, a cache memory, and a storage apparatus, the storage system being coupled to a host computer in a manner that allows communication between the storage system and the host computer,
wherein the storage apparatus has a storage area comprising a first logical volume and a second logical volume, and
wherein the processor is configured to:
store, in the cache memory, new data when a write request to write the new data in the first logical volume is received after reception of a first pair creating request, which is for storing, in the second logical volume, the same data that is stored in the first logical volume at present; and
omit copying, to the second logical volume, data that is in the first logical volume at a time of reception of the first pair creating request when the data that is in the first logical volume at the time of reception of the first pair creating request is stored in the cache memory and is not copied to the second logical volume yet at a time of reception of a second pair creating request for storing present data of one of the first logical volume and the second logical volume in another of the first logical volume and the second logical volume.

### Claim 2 (depends on 1)

The storage system according to claim 1,
wherein the first logical volume has a storage area comprising a unit area, the second logical volume has a storage area comprising a unit area, and the unit area of the first logical volume and the unit area of the second logical volume correspond to each other,
wherein a storage area of the cache memory comprises a first side and a second side, which are associated with each other, and
wherein the processor is configured to:
store the new data, when the write request to write the new data in the unit area of the first logical volume is received after the reception of the first pair creating request and before data that is in the unit area of the first logical volume at the time of reception of the first pair creating request is copied to the second logical volume, in the second side that is associated with the first side where the data that is in the unit area of the first logical volume at the time of reception of the first pair creating request is stored; and
copy, to the second logical volume, present data in the unit area of the first logical volume that is generated by combining the data stored on the first side and the data stored on the second side, instead of copying the data stored on the first side to the second logical volume, when the new data is stored on the second side and the data on the first side is not copied to the second logical volume yet at a time of reception of a second pair creating request for storing, in the second logical volume, the same data that is stored at present in the first logical volume.

### Claim 3 (depends on 2)

The storage system according to claim 2,
wherein the processor memory is configured to hold copy information and update information, the copy information indicating whether or not data that is in the unit area of the first logical volume at the time of reception of the first pair creating request has been copied to the second logical volume, the update information indicating whether or not the write request to write the new data to the unit area of the first logical volume has been received after the reception of the first pair creating request, and
wherein the processor is configured to:
avoid copying the data stored on the first side to the second logical volume when it is determined, based on the copy information and the update information, that data in the unit area of the first logical volume is already copied to the second logical volume and the request to write the new data to the unit area of the first logical volume is not received yet at the time of reception of the second pair creating request;
copy the data stored on the first side to the second logical volume when it is determined, based on the copy information and the update information, that data in the unit area of the first logical volume is not copied to the second logical volume yet and the write request to write the new data to the unit area of the first logical volume is not received yet at the time of reception of the second pair creating request;
copy, to the second logical volume, present data in the unit area of the first logical volume that is generated by combining the data stored on the first side and the data stored on the second side, when it is determined, based on the copy information and the update information, that data in the unit area of the first logical volume is already copied to the second logical volume and the write request to write the new data to the unit area of the first logical volume is already received at the time of reception of the second pair creating request; and
copy, to the second logical volume, present data in the unit area of the first logical volume that is generated by combining the data stored on the first side and the data stored on the second side, instead of copying the data stored on the first side to the second logical volume, when it is determined, based on the copy information and the update information, that data in the unit area of the first logical volume is not copied to the second logical volume yet and the write request to write the new data to the unit area of the first logical volume is already received at the time of reception of the second pair creating request.

### Claim 4 (depends on 1)

The storage system according to claim 1,
wherein the first logical volume has a storage area comprising a unit area, the second logical volume has a storage area comprising a unit area, and the unit area of the first logical volume and the unit area of the second logical volume correspond to each other,
wherein a storage area of the cache memory comprises a first side and a second side, which are associated with each other, and
wherein the processor is configured to:
store the new data, when the write request to write the new data in the unit area of the first logical volume is received after the reception of the first pair creating request and before data that is in the unit area of the first logical volume at the time of reception of the first pair creating request is copied to the second logical volume, in the second side that is associated with the first side where the data that is in the unit area of the first logical volume at the time of reception of the first pair creating request is stored; and
discard data stored on the second side, instead of copying the data stored on the first side to the second logical volume, when the new data is stored on the second side and the data on the first side is not copied to the second logical volume yet at a time of reception of a second pair creating request for storing, in the first logical volume, the same data that is in the second logical volume at present.

### Claim 5 (depends on 4)

The storage system according to claim 4,
wherein the processor memory is configured to hold copy information, which indicates whether or not data that is in the unit area of the first logical volume at the time of reception of the first pair creating request has been copied to the second logical volume, and
wherein the processor is configured to:
copy, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume when it is determined, based on the copy information, that the data in the unit area of the first logical volume is already copied to the second logical volume at the time of reception of the second pair creating request;
avoid copying, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume when it is determined, based on the copy information, that the data in the unit area of the first logical volume is not copied to the second logical volume yet at the time of reception of the second pair creating request; and
discard the data stored on the second side when it is determined, based on the copy information, that the data in the unit area of the first logical volume is not copied to the second logical volume yet at the time of reception of the second pair creating request, and when the new data is stored on the second side.

### Claim 6 (depends on 4)

The storage system according to claim 4,
wherein the processor memory is configured to hold copy information and update information, the copy information indicating whether or not data that is in the unit area of the first logical volume at the time of reception of the first pair creating request has been copied to the second logical volume, the update information indicating whether or not the write request to write the new data to the unit area of the first logical volume has been received after the reception of the first pair creating request, and
wherein the processor is configured to:
copy, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume, when it is determined, based on the copy information and the update information, that the data in the unit area of the first logical volume is already copied to the second logical volume and the write request to write the new data to the unit area of the first logical volume is already received at the time of reception of the second pair creating request;
avoid copying, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume, when it is determined, based on the copy information and the update information, that the data in the unit area of the first logical volume is already copied to the second logical volume and the write request to write the new data to the unit area of the first logical volume is not received yet at the time of reception of the second pair creating request;
avoid copying, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume, when it is determined, based on the copy information and the update information, that the data in the unit area of the first logical volume is not copied to the second logical volume yet at the time of reception of the second pair creating request; and
discard the data stored on the second side when it is determined, based on the copy information and the update information, that the data in the unit area of the first logical volume is not copied to the second logical volume yet at the time of reception of the second pair creating request, and when the new data is stored on the second side.

### Claim 7

A control method for a storage system,
the storage system comprising a processor, a processor memory, a cache memory, and a storage apparatus, the storage system being coupled to a host computer in a manner that allows communication between the storage system and the host computer,
the storage apparatus having a storage area comprising a first logical volume and a second logical volume,
the control method comprising:
a first step of storing, by the processor, in the cache memory, new data when a write request to write the new data in the first logical volume is received after reception of a first pair creating request, which is for storing, in the second logical volume, the same data that is stored in the first logical volume at present; and
a second step of omitting copying, by the processor, to the second logical volume, data that is in the first logical volume at a time of reception of the first pair creating request when the data that is in the first logical volume at the time of reception of the first pair creating request is stored in the cache memory and is not copied to the second logical volume yet at a time of reception of a second pair creating request for storing present data of one of the first logical volume and the second logical volume in another of the first logical volume and the second logical volume.

### Claim 8 (depends on 7)

The control method according to claim 7,
wherein the first logical volume has a storage area comprising a unit area, the second logical volume has a storage area comprising a unit area, and the unit area of the first logical volume and the unit area of the second logical volume correspond to each other,
wherein a storage area of the cache memory comprises a first side and a second side, which are associated with each other,
wherein the first step comprises storing, by the processor, the new data, when the write request to write the new data in the unit area of the first logical volume is received after the reception of the first pair creating request and before data that is in the unit area of the first logical volume at the time of reception of the first pair creating request is copied to the second logical volume, in the second side that is associated with the first side where the data that is in the unit area of the first logical volume at the time of reception of the first pair creating request is stored, and
wherein the second step comprises copying, by the processor, to the second logical volume, present data in the unit area of the first logical volume that is generated by combining the data stored on the first side and the data stored on the second side, instead of copying the data stored on the first side to the second logical volume, when the new data is stored on the second side and the data on the first side is not copied to the second logical volume yet at a time of reception of a second pair creating request for storing, in the second logical volume, the same data that is stored at present in the first logical volume.

### Claim 9 (depends on 8)

The control method according to claim 8,
wherein the processor memory is configured to hold copy information and update information, the copy information indicating whether or not data that is in the unit area of the first logical volume at the time of reception of the first pair creating request has been copied to the second logical volume, the update information indicating whether or not the write request to write the new data to the unit area of the first logical volume has been received after the reception of the first pair creating request, and
wherein the second step comprises:
avoiding copying, by the processor, the data stored on the first side to the second logical volume when it is determined, based on the copy information and the update information, that data in the unit area of the first logical volume is already copied to the second logical volume and the request to write the new data to the unit area of the first logical volume is not received yet at the time of reception of the second pair creating request;
copying, by the processor, the data stored on the first side to the second logical volume when it is determined, based on the copy information and the update information, that data in the unit area of the first logical volume is not copied to the second logical volume yet and the write request to write the new data to the unit area of the first logical volume is not received yet at the time of reception of the second pair creating request;
copying, by the processor, to the second logical volume, present data in the unit area of the first logical volume that is generated by combining the data stored on the first side and the data stored on the second side, when it is determined, based on the copy information and the update information, that data in the unit area of the first logical volume is already copied to the second logical volume and the write request to write the new data to the unit area of the first logical volume is already received at the time of reception of the second pair creating request; and
copying, by the processor, to the second logical volume, present data in the unit area of the first logical volume that is generated by combining the data stored on the first side and the data stored on the second side, instead of copying the data stored on the first side to the second logical volume, when it is determined, based on the copy information and the update information, that data in the unit area of the first logical volume is not copied to the second logical volume yet and the write request to write the new data to the unit area of the first logical volume is already received at the time of reception of the second pair creating request.

### Claim 10 (depends on 7)

The control method according to claim 7,
wherein the first logical volume has a storage area comprising a unit area, the second logical volume has a storage area comprising a unit area, and the unit area of the first logical volume and the unit area of the second logical volume correspond to each other,
wherein a storage area of the cache memory comprises a first side and a second side, which are associated with each other,
wherein the first step comprises storing, by the processor, the new data, when the write request to write the new data in the unit area of the first logical volume is received after the reception of the first pair creating request and before data that is in the unit area of the first logical volume at the time of reception of the first pair creating request is copied to the second logical volume, in the second side that is associated with the first side where the data that is in the unit area of the first logical volume at the time of reception of the first pair creating request is stored, and
wherein the second step comprises discarding, by the processor, data stored on the second side, instead of copying the data stored on the first side to the second logical volume, when the new data is stored on the second side and the data on the first side is not copied to the second logical volume yet at a time of reception of a second pair creating request for storing, in the first logical volume, the same data that is in the second logical volume at present.

### Claim 11 (depends on 10)

The control method according to claim 10,
wherein the processor memory is configured to hold copy information, which indicates whether or not data that is in the unit area of the first logical volume at the time of reception of the first pair creating request has been copied to the second logical volume, and
wherein the second step comprises:
copying, by the processor, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume when it is determined, based on the copy information, that the data in the unit area of the first logical volume is already copied to the second logical volume at the time of reception of the second pair creating request;
avoiding copying, by the processor to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume when it is determined, based on the copy information, that the data in the unit area of the first logical volume is not copied to the second logical volume yet at the time of reception of the second pair creating request; and
discarding, by the processor, the data stored on the second side when it is determined, based on the copy information, that the data in the unit area of the first logical volume is not copied to the second logical volume yet at the time of reception of the second pair creating request, and when the new data is stored on the second side.

### Claim 12 (depends on 10)

The control method according to claim 10,
wherein the processor memory is configured to hold copy information and update information, the copy information indicating whether or not data that is in the unit area of the first logical volume at the time of reception of the first pair creating request has been copied to the second logical volume, the update information indicating whether or not the write request to write the new data to the unit area of the first logical volume has been received after the reception of the first pair creating request, and
wherein the second step comprises:
copying, by the processor, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume when it is determined, based on the copy information and the update information, that the data in the unit area of the first logical volume is already copied to the second logical volume and the write request to write the new data to the unit area of the first logical volume is already received at the time of reception of the second pair creating request;
avoiding copying, by the processor, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume when it is determined, based on the copy information and the update information, that the data in the unit area of the first logical volume is already copied to the second logical volume and the write request to write the new data to the unit area of the first logical volume is not received yet at the time of reception of the second pair creating request;
avoiding copying, by the processor, to the first logical volume, data in the unit area of the second logical volume that corresponds to the unit area of the first logical volume when it is determined, based on the copy information and the update information, that the data in the unit area of the first logical volume is not copied to the second logical volume yet at the time of reception of the second pair creating request; and
discarding, by the processor, the data stored on the second side when it is determined, based on the copy information and the update information, that the data in the unit area of the first logical volume is not copied to the second logical volume yet at the time of reception of the second pair creating request, and when the new data is stored on the second side.