JP2011232962A - Disk array device and method for controlling mirrored cache - Google Patents

Abstract

A disk array device capable of performing mirrored cache control using only a standard HDD connection bus without requiring a complicated hardware configuration.
In a disk array device, a cache memory storing write data from a host device and a flash memory drive SSD (Solid State Drive) having a recording capacity more than twice the mounting capacity of the cache memory are mounted. In a configuration where the controller is duplicated, cache memory data on one controller is written as mirrored data to the flash memory drive, and managed as cache memory mirrored data on both controllers, thereby improving data redundancy between controllers. Makes it possible to maintain.
[Selection] Figure 1

Description

  The present invention relates to a disk array device and a mirrored cache control method.

Some recent disk array devices constitute a device with a built-in duplex controller including a duplex controller that can be connected to different host devices. In this type of disk array device, data transfer is possible between each controller and the corresponding host device. Each controller is provided with a cache memory for temporarily storing data transferred to and from the host device. The host device and the disk array device are connected by an FC interface or a SCSI interface, and the disk array device receives an IO request from the host device, and accesses by transferring data according to the request. Normally, these interfaces are connected one-to-one between the host device and the disk array device. When there is one interface connecting the host device and the disk array device, the access performance depends on the type of interface to be connected. Further, when a failure occurs in the interface to be connected, it becomes inaccessible unless another alternative path is provided.

As one of the technologies to improve these, the access path from the host device to the disk array device is connected with two interfaces, and even if one becomes unusable, the remaining one keeps accessing. There is technology. By using this access path redundancy, even if a failure occurs in one controller, the access can be continued without stopping the system operation by switching the access path to the other controller.

In addition, the controller is equipped with a cache memory that mediates data transfer between the host device and the logical disk. By temporarily holding the data in the logical disk, high-speed data transfer with the host device is possible. Is possible. The controller sends a write completion response to the host device when the write data from the host device is temporarily stored in the cache memory. Thereafter, high-speed access is realized by writing data in the cache memory to the logical disk. This method is generally called a write back cache (WBC). Write data from the host device is stored in the cache memory of the controller and then stored as mirrored data in the cache memory of another controller. In this way, even when a failure occurs in one controller, the mirrored data stored in the other controller can be taken over, and the cache memory can be made redundant with respect to the controller failure. For example, when a failure occurs in the first controller, the access path from the host device is switched to the second controller side, and all write data from the host device is stored in its own cache memory. At this time, since the data stored in the own cache memory of the first controller is also stored in the other controller's cache memory, access can be taken over without losing the write data from the host device. it can.

For example, as disclosed in Patent Document 1, in a disk array apparatus incorporating the above-described dual controller, a so-called mirrored cache system is adopted in order to improve the data integrity of the cache memory in each controller. There is something that is. This method is a method of copying (mirroring) write data received from the host device by the own system controller to the cache memory of the other system controller.

JP 2001-43026 A

  However, as described above, in the conventional disk array device (duplex controller built-in device) that incorporates the duplex controller and applies the mirrored cache method, both the buses other than the standard connection bus to the drive device are required. It is necessary to provide a dedicated bus for connecting the controllers, and there are problems that the number of hardware components increases, the control becomes complicated, and at the same time, the cost increases. Further, it is necessary to halve the cache memory area for the mirrored cache, and there is a problem that the cache memory area cannot be used efficiently.

  The present invention has been made to solve the above-described problems. By performing mirrored cache control using only a standard drive device connection bus, a complicated hardware configuration is not required, and cache memory can be efficiently used. An object of the present invention is to provide a disk array device that can be used.

To solve the above problem,
The disk array device according to the present invention stores first and second cache memories that temporarily store write data from a host device to a data storage medium, and the first cache memory and the second cache memory. A drive device that stores mirrored data of write data to be performed, a first controller that includes the first cache memory, and that performs mirrored cache control between the first cache memory and the drive device;
A second controller that includes the second cache memory and that performs mirrored cache control between the second cache memory and the drive device, wherein the drive device stores a write stored in the first cache memory. For storing mirrored data of data, for storing mirrored data of write data stored in the first storage area that is greater than or equal to the capacity of the first cache memory and the second cache memory, An SSD (Solid State Drive) having a second storage area that is greater than or equal to the capacity of the second cache memory;
A mirrored cache control method for a disk array device according to the present invention includes:
The disk array device includes first and second cache memories, first and second controllers, and a drive device composed of an SSD having first and second storage areas, from a host device to a data storage medium. Temporarily storing the write data of the write data in the first cache memory, and the first controller has mirror data of the write data stored in the first cache memory at a capacity greater than or equal to the capacity of the first cache memory. A step of storing in the first storage area; a step of temporarily storing write data from a host device to the data storage medium in a second cache memory; and the second controller comprising: The second storage area in which the mirrored data of the write data stored in the cache memory is greater than or equal to the capacity of the second cache memory. Characterized by a step of storing the.

  According to the present invention, it is possible to provide a disk array apparatus capable of performing mirrored cache control only by a connection bus to a standard drive device without requiring a complicated hardware configuration.

1 is a block diagram showing a configuration of a disk array device in a first embodiment. The figure which shows an example of the division | segmentation of the storage area of SSD divided and allocated in 1st Embodiment. The block diagram which shows the structure of the disk array apparatus in 2nd Embodiment. The figure which shows an example of the division | segmentation of the storage area of SSD in 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  First, the structure of the disk array device of this embodiment will be described with reference to FIGS.

FIG. 1 is a block diagram showing the overall configuration of the disk array device 10 of the present embodiment. The disk array device 10 is connected to host devices 17 and 170, which are host devices, via a fiber channel (FC) interface or a small computer system interface (SCSI or squeegee) interface. The connection path 18 connects the disk array device 10 to the host device, the aggregate thereof, or another data storage device. Although two host devices connected to the disk array device 10 are illustrated in FIG. 1, one or more host devices may be used. Further, although there are various connection forms, in this embodiment, the connection form does not matter, so the FC interface is collectively used.

  The disk array device 10 has two or more disk array controllers (hereinafter simply referred to as controllers) that perform various processes. In this embodiment, the disk array apparatus 10 includes a first controller 11 and a second controller 110. Each of the first controller 11 and the second controller 110 is connected to a drive device that is a data storage medium via a drive device connection bus. In this embodiment, a hard disk drive (HDD) 19 and a solid state drive (SSD) 20 are provided as drive devices. The number of HDDs 19 is one in FIG. Further, a logical disk (LU) may be configured by one or a plurality of HDDs.

The first controller 11 includes a microprocessor 13 that performs “mirrored cache processing” described later on the HDD 19 and the SSD 20 that are drive devices, a memory 14, a host interface 12 that connects the host device and the first controller 11, and A disk interface 15 that connects the drive device and the first controller 11, and a cache memory 16 that serves as a buffer in an input / output request to the drive device from the host device 17 via the connection path 18 are provided. For example, in the writing process from the host device to the drive device, entry into the cache memory 16 is made and a write completion response is returned to the requesting host device. Subsequently, writing is performed from the cache memory to the drive device. Further, in the reading process from the host device to the drive device, it is determined whether or not data is entered in the cache memory 16. If the entry is made in the cache memory 16, the data is returned. If the entry is not made in the cache memory 16, the data is read from the drive device to the cache memory 16, and then the data read to the cache memory 16 is sent to the host device The operations of the symbols 120, 130, 140, and 150 in response to 17 are the same as the operations of the symbols 12, 13, 14, and 15 in the first controller 11.

FIG. 2 is a diagram showing the storage area 200 of the SSD 20 divided and assigned. As shown in FIG. 2, the storage area of the SSD 20 stores the data storage area 202 storing the mirrored cache data in the first controller 11, the storage area 201, and the mirrored cache data in the second controller 110. The storage area 202 is divided. The first mirrored cache data storage area 201 and the second mirrored cache data storage area are larger than the capacity of the cache memories 16 and 160, respectively. In the present embodiment, since the cache memory 16 and the cache memory 160 have the same capacity, the SSD 20 has a capacity that is at least twice that of the cache memory 16. In this way, by dividing the area of the SSD 20 into the storage area 201 and the storage area 202, mirrored cache data (hereinafter referred to as mirrored data) of both controllers is held.

The operation of the disk array device 10 when data mirrored cache control is performed when the host device 17 accesses the disk array device 10 will be described below.

When data is written from the host device 17 to the HDD 19, the write data is stored in the cache memory 16 of the first controller 11. Thereafter, the data (mirrored data) is written into the first controller mirrored cache data storage area 201 of the SSD 20 corresponding to the address of the write data stored in the cache memory 16. In this embodiment, mirrored data is written every time a write access from the host device 17 is made. Note that when data is written from the host device 170 to the HDD 19, the write data is stored in the cache memory 160 of the second controller 110. Thereafter, the data (mirrored data) is written into the second controller mirrored cache data storage area 202 of the SSD 20 corresponding to the address of the write data stored in the cache memory 160.

When a failure occurs in the first controller 11 and access from the host device 17 to the HDD 19 becomes impossible, the write data at that time is stored in the cache memory 16 and the SSD 20 of the first controller 11. It will be in the state.

In the second controller 110, when the failure of the first controller 11 is detected, the write data in the cache memory 160 is moved to the HDD 19 and stored in the first controller mirrored cache data storage area 201 of the SSD 20. The mirrored data of the controller 11 is read. Thereafter, the data is guaranteed by writing to the HDD 19.

According to the present embodiment, a mirrored cache control is performed only by a standard drive device connection bus, so that a complicated hardware configuration is not required, and a cache memory can be used efficiently. An apparatus and a mirrored cache control method can be provided.

  The present invention is not limited to the above-described embodiment, and the design may be changed without departing from the gist of the invention.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and description is abbreviate | omitted.

FIG. 3 is a diagram showing a configuration of the disk array device 10 in the present embodiment. In the present embodiment, the SSD 20 has a logical disk area 191 and a mirrored cache memory area 192 for storing mirrored data.

That is, the storage area 300 of the SSD 20 is divided into a mirrored cache memory area 192 that stores mirrored cache data and a logical disk area 191 that is an area for a logical disk. FIG. 4 shows an example of division of the storage area 300 of the SSD 20 in the present embodiment. The storage area 300 includes a first controller mirrored cache data storage area 301, a second controller mirrored cache data storage area 302, and a logical disk area 303. The storage area 301 and the storage area 302 have storage areas that exceed the capacity of the cache memory provided in each controller.

When data is written from the host device 17 to the disk array device 10, the write data is stored in the cache memory 16 of the first controller 11. Thereafter, the data (mirrored data) is written into the first controller mirrored cache data storage area 301 of the SSD 20 corresponding to the address of the write data stored in the cache memory 16. In this embodiment, mirrored data is written every time a write access from the host device 17 is made. When data is written from the host device 170 to the disk array device 10, the write data is stored in the cache memory 160 of the second controller 110. Thereafter, the data (mirrored data) is written into the second controller mirrored cache data storage area 302 of the SSD 20 corresponding to the address of the write data stored in the cache memory 160.

Data stored in the cache memory 16 by write access from the host device 17 is written to the HDD 19 by write back processing. For example, when using an on-memory database, the database is stored in the logical disk area 303.

As described above, in the present embodiment, the database is defined in the logical disk area configured in the SSD and data is stored, so that high-speed data access is possible by high-speed seek operation and data transfer. Further, if the read access is not performed only by the write access, it can be used as a database backup.

DESCRIPTION OF SYMBOLS 10 ... Disk array apparatus 11, 110 ... Controller, 12, 120 ... Host apparatus interface, 13, 130 ... Microprocessor, 14, 140 ... Memory, 15, 150 ... Disk interface, 16, 160 ... Cache memory, 17, 170 ... Host device, 18 ... Connection path, 19 ... Hard disk drive (HDD), 20 ... Solid State Drive (SSD)

Claims (5)

First and second cache memories for temporarily storing write data from the host device to the data storage medium;
A drive device for storing mirrored data of write data stored in the first cache memory and the second cache memory;
A first controller comprising the first cache memory, and performing a mirrored cache control between the first cache memory and the drive device;
A second controller comprising the second cache memory and performing a mirrored cache control between the second cache memory and the drive device;
With
The drive device is
For storing mirrored data of write data stored in the first cache memory, a first storage area that is greater than or equal to the capacity of the first cache memory;
This is for storing mirrored data of write data stored in the second cache memory, and is an SSD (Solid State Drive) having a second storage area that is greater than or equal to the capacity of the second cache memory. A featured disk array device. The second controller is
2. The disk array device according to claim 1, wherein mirrored data stored in a first storage area of the drive device is read into the second cache memory based on detection of a failure of the first controller. . The drive device is
3. The disk array device according to claim 1, further comprising a logical disk area accessible from the host device. In the mirrored cache control method of a disk array device, the disk array device includes a first and second cache memory, a first and second controller, and a drive device comprising an SSD having first and second storage areas. With
Temporarily storing write data from the host device to the data storage medium in the first cache memory;
The first controller stores the mirrored data of the write data stored in the first cache memory in the first storage area that is greater than or equal to the capacity of the first cache memory;
Temporarily storing write data from the host device to the data storage medium in a second cache memory;
The second controller has a step of storing mirrored data of write data stored in the second cache memory in the second storage area that is equal to or larger than a capacity of the second cache memory. Mirrored cache control method for disk array device. The second controller detecting a failure of the first controller;
When a failure is detected in the detecting step,
Writing the write data stored in the second cache memory to the data storage medium by the second controller;
5. The mirrored cache control method for a disk array device according to claim 4, further comprising: reading the mirrored data stored in the first storage area into the second cache memory. .