JP2000148587A - Storage device and method for determining storage area - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of an access by determining a storage area suited to the contents of an access to a storage area and using the determined storage area. SOLUTION: A cache memory 4 is provided with two sorts of cache memories 4a, 4b having respectively different page sizes and these cache memories 4a, 4b are properly used in accordance with the sort of an access from a host computer 1 or the quantity of data for the access. In the case of accessing data of large capacity when the cache memory 4b having large page size is used, the umber of cache pages to be opened can be reduced. In the case of a sequential access, the efficiency of a cache can be improved by prereading data supposed to be accessed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage device and a storage area switching method, and more particularly to a method for performing a predetermined access to predetermined data stored in a plurality of storage areas having different storage capacities. The present invention also relates to a storage device that determines a storage area corresponding to this access, and executes a process corresponding to the access in the determined storage area, and a storage area determination method.

[0002]

2. Description of the Related Art Conventionally, as this type of storage device, one disclosed in Japanese Patent Application Laid-Open No. 6-44139 is known. In this publication, a storage device is a disk cache system using a cache memory, which includes a volatile semiconductor memory for storing read data and a nonvolatile semiconductor memory for storing write data. . Then, in response to the read request or the write request, the access destination semiconductor memory is allocated. At this time, when replacing pages based on the LRU, a memory control unit is provided which controls the write-back of unwritten non-matched pages of data in the external storage device by a predetermined number of consecutive times.

[0003]

In the above-mentioned conventional storage device, the memory is switched in response to a read request or a write request, but the data in the read request or the write request is not changed regardless of the capacity. Since data is read or written to or from a single memory, there is a problem that the memory cannot be used efficiently.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to determine a storage area suitable for the contents of access to a storage area and to improve access efficiency by using the determined storage area. It is an object of the present invention to provide a possible storage device and a storage area determination method.

[0005]

In order to achieve the above object, the invention according to claim 1 comprises a plurality of storage areas having different storage capacities for storing predetermined data; Access means for executing read and write access, and access input determination for determining whether the access is a sequential access or a random access while receiving the access from the access means, and determining a data size corresponding to the access Means for determining a predetermined storage area from a plurality of storage areas in accordance with an access by the access means determined while input by the access input determination means, and switching to the determined storage area. There is a configuration.

In the invention according to claim 1 configured as described above, the storage device includes a storage area having a plurality of areas having different storage capacities as a storage area for storing predetermined data. Here, access for reading and writing of predetermined data is executed from the access means, and when this access is input by the access input determining means, the access input determining means determines whether the access is a random access or a sequential access. And the data size due to this access is determined. The storage area determining means selects an appropriate storage area from a plurality of storage areas having different sizes according to the contents of access and the data size determined by the access input determining means. Or reading or writing of predetermined data corresponding to.

That is, a storage area having a size suitable for access is selected from a plurality of storage areas having different sizes, and reading or writing is performed in the selected storage area, so that the storage area is efficiently provided. Can be used.

[0008] The invention according to claim 2 is based on claim 1.
In the storage device described in (1), when the access input by the access unit is a random access, the access input determining unit detects a data size corresponding to the random access.

In the invention according to claim 2 configured as described above, when the access input by the access means is random access, the data size of data corresponding to the random access is detected. .

Thus, when this data exists in the first storage area, it becomes possible to select a storage area having an area suitable for the data size from the plurality of first storage areas. Therefore, the invention according to claim 3 is based on claim 2
In the storage device according to the above, when the access input determination means determines that data corresponding to the access is stored in the storage area, the storage area determination means,
A predetermined storage area is determined from a plurality of storage areas based on the detected data size.

In the invention according to claim 3 configured as described above, when the access input determining means determines that the data corresponding to the access is stored in the storage area, the storage area determining means performs the detection. A predetermined storage area is determined from the plurality of storage areas based on the obtained data size.

As a specific example of configuring the storage area, the invention according to claim 4 is the storage device according to any one of claims 1 to 3, wherein the storage area is configured by a cache memory. I have. In the invention according to claim 4 configured as described above, the number of cache memories constituting the storage area may be plural, and the size thereof can be changed as appropriate.

According to a fifth aspect of the present invention, in the storage device according to the fourth aspect, the cache memory is configured so that boundaries of a plurality of storage areas can be changed. In the invention according to claim 5 configured as described above, the cache memory includes a plurality of storage areas having different sizes, and by changing boundaries of the plurality of storage areas according to the situation, the size of each storage area is reduced. It can be changed as needed.

As described above, when a predetermined access is performed to predetermined data stored in a plurality of storage areas having different storage capacities, a storage area corresponding to the access is determined, and the determined storage area is determined. The method of determining a storage area for executing a process corresponding to an access in the storage area is not necessarily limited to a substantial device, and it can be easily understood that the method also functions as the method.

Therefore, according to the present invention, when a predetermined access is performed to predetermined data stored in a plurality of storage areas having different storage capacities, the storage area corresponding to the access is changed. A method for determining a storage area for executing a process corresponding to an access in the determined storage area, comprising: a plurality of storage areas having different storage capacities for storing predetermined data; An access step of executing read and write access to predetermined data; determining whether the access is a sequential access or a random access while inputting the access from the access step; and determining a data size corresponding to the access. Access input discriminating step, and an access process discriminated while inputting in the access input discriminating step. And it determines the predetermined storage area of a plurality of storage areas in response to the access by, it is constituted comprising a storage area determination step of using the determined storage area corresponding to this access. That is, there is no difference that the method is not necessarily limited to a substantial device and is effective as a method.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a memory system to which a storage device according to an embodiment of the present invention is applied. In FIG. 1, the memory system comprises a host computer 1, a host adapter 2, a cache controller 3, a cache memory 4, a directory area 5, a disk adapter 6, and a hard disk 7. Here, the host adapter 2 is an interface between the host computer 1 and the cache memory 4, and controls data transfer between the host computer 1 and the cache memory 4.

When a read request or a write request is accessed from the host computer 1, the directory area 5 checks whether the data associated with the access is stored in the hard disk 6 or the cache memory 4, and The following information is confirmed. (1) Data type (whether data has already been written to the disk, etc.). (2) What is the size of the written data? (3) Which cache page is currently being accessed. (4) Where is the start address of each cache page?

That is, the directory area 5 has a function of managing information necessary for searching the cache page 4. In the present embodiment, the cache memory 4 has a storage capacity of two types of cache pages of 8 KB and 64 KB.
a, 4b.

The cache controller 3
This directory area 5 is referred to, and it is checked whether data exists in the cache memory 4. Then, if the accessed data exists in the cache memory 4 (cache hit), the corresponding data is transferred from the cache memory 4 to the host computer 1.
Therefore, data transfer accompanying access from the host computer 1 can be realized at high speed.

If there is no data on the cache memory 4 (cache miss), the cache controller 3 controls a portion called a disk adapter 6 which controls data transfer between the hard disk 7 and the cache memory 4. Via the host adapter 2, the acquired data is transferred to the host computer 1 via the host adapter 2.
At this time, the cache controller 3 stores the data acquired from the hard disk 7 in one of the cache memories 4a and 4b while referring to the history of the access of the host computer 1 so far. . Thus, when the same data is accessed from the host computer 1 thereafter, the data stored in one of the cache memories 4a and 4b can be transferred to the host computer 1.

Therefore, the cache memories 4a and 4b
Constitutes a storage area, and the host computer 1
And the host adapter 2 constitute an access means, the cache controller 3 constitutes a storage area determining means,
The directory area 5 constitutes an access input determining means.

Next, the operation of the present embodiment will be described with reference to FIGS. First, the process of determining whether to use the cache memory 4b having a large page size or the cache memory 4a having a small page size will be described with reference to the flowchart of FIG.

Referring to FIG. 2, the system waits for reception of an access command for a read request or a write request from the host computer 1 and receives a predetermined request for deciding which of the page sizes of the cache memories 4a and 4b to use. It waits (step A1). And
When the access command is received, it is determined whether the predetermined request is a sequential access or a random access (step A2). This is because the cache memories 4a and 4b are selected by the sequential access and the random access. At this time, the cache controller 3 determines which access method is used, that is, whether it is a sequential access or a random access, by referring to a history of accesses from the host computer 1 so far (step A2).

If it is determined that the access is a sequential access, the cache memory 4b having a large page size is employed, and the required data is smaller than the cache page as shown in FIG. In this case, by reading ahead the data around the necessary data that is expected to be accessed in the future, it is possible to increase the cache efficiency because a cache hit occurs when the access to the pre-read data matches. it can. When it is determined that the access is a sequential access, data of a page size is transferred to the cache memory 4b (step A3).

In such a case, in the cache memory 4b, in consideration of changing the boundary between the cache memory 4a and the cache memory 4b having the cache size of the cache memory 4b, priority is given to the cache page farthest from the boundary. To use. by the way,
In random access, since the probability of accessing the same cache page before the cache page is rewritten is low, the number of pages becomes insufficient, and the number of times that the page read ahead in anticipation of future access must be rewritten is reduced. Thus, reducing the page size and increasing the number of pages increases the cache efficiency. On the other hand, when the data is large, the amount of the page size to be opened increases, and the efficiency cannot be improved.

If it is determined in step A2 that the access is a random access, the cache memory 4b having a large page size is employed, and it is determined whether the data size is half or more of the page size (step A2). A4). However, in the case of random access, as shown in FIG. 4, when there is a portion where the amount of data is smaller than the cache page size and there is no data, the data may be read ahead like a sequential file.
Since it is unlikely that data on the same page will be accessed before the page is rewritten, prefetching is not performed and only necessary data is transferred.

Here, when the data size is half or more of the page size, a large page is used. However, it is more efficient to use the large page size cache memory 4b by sequential access, so that it is more efficient. , Unnecessary pages (pages that have been in use for a long time since they were last accessed, pages that are accessed infrequently, pages that are temporarily created by random access, pages that are near the border with different sizes, etc. )
It is checked whether or not there is (step A5). If there is an unnecessary page, the cache memory 4b having a large page size is used (step A3).

On the other hand, when the amount of the large page size is less than half or when it is determined that there is no unnecessary page in the large page size cache memory 4b, the small page size cache memory 4a is used (step). A6). Next, an unnecessary page ratio of each page size (a ratio of the number of pages determined to be erasable) is obtained (step A7), and the cache memory 4a having the small page size is replaced with the cache memory having the large page size. If the unnecessary page rate is considerably larger than that of 4b, the page size boundary is changed so that the amount of unnecessary pages having a small page size is reduced (step A8).

Similarly, when the unnecessary page rate of the large page size is considerably larger than that of the small page size, the unnecessary page size of the large page size is reduced so that the unnecessary page amount is reduced. The size boundary is changed (step A9).

On the other hand, if there is not much difference between the unnecessary page rate of the small page size and the unnecessary page rate of the large page size, the process is terminated without changing the page size boundary.

Next, each operation when a read request or a write request is accessed from the host computer 1 will be described with reference to FIG. First, the operation when a read request access occurs will be described. In the figure, a command is received from the host computer 1 (step B1), and it is confirmed whether or not the command is a read request command (step B2). When the command of the read request is confirmed, whether or not the data exists in the cache memory 4 is searched with reference to the directory areas 5 of the cache memories 4a and 4b of the respective sizes (step B3). If the data exists in the cache memory 4, the data is transferred from the cache memory 4 to the host computer 1 (step B6).

On the other hand, if the data does not exist in the cache memory 4, the above-mentioned "process for determining whether to use the cache memory 4b having a large page size or the cache memory 4a having a small page size" is described above. And the cache memories 4a and 4b to be used
Is determined (step B5). At this time, data is transferred from the hard disk 7 to the determined cache memories 4a and 4b (step B9), and the directory area 5 is updated (step B11).

Next, the operation when a write request access occurs will be described. In the figure, a command is received from the host computer 1 (step B1),
It is checked whether the command is a write request command (step B2). Then, when it is confirmed that the command is a write request command, it is determined whether data exists in the cache memory 4 or not.
The search is performed with reference to the directory area 5 of step b (step B4).

If the data exists in the cache memory 4, the data is transferred from the cache memory 4 to the host computer 1 (step B7).

On the other hand, if the data does not exist in the cache memory 4, the above-mentioned "process for determining whether to use the cache memory 4b having a large page size or the cache memory 4a having a small page size" is described above. And the cache memories 4a and 4b to be used
Is determined (step B8). At this time, the host computer 1 stores the determined cache memories 4a and 4b.
(Step B10), the directory area 5 is updated (step B12), and the contents changed by the disk adapter 6 with respect to the hard disk 7 in view of the timing (step B13).

In this embodiment, the cache memories 4a and 4b having different page sizes have 8 KB,
Although a cache page of 64 KB is employed, of course, the cache memories 4a, 4
The size is not limited to b, and can be changed to any size suitable for the memory system.

Although the present embodiment employs a configuration in which the cache memories 4a and 4b having two types of page sizes are used, it is needless to say that the present invention is not limited to such two types of memory. Any number of page sizes suitable for the system may be used.

Further, in the case of random access as described above, in step A4 shown in FIG. 2, the amount of data used to determine which page size to use is more efficient depends on the memory system. Needless to say, they are different. Therefore, the amount of data used for this determination can be changed as appropriate.

As described above, two types of cache memories 4a, 4a,
4b, the cache memories 4a and 4b are selectively used in accordance with the type of access from the host computer 1 and the amount of data accompanying the access, so that when the cache memory 4b having a large page size is used, a large capacity In the case of data access, the number of open cache pages can be reduced,
In the case of sequential access, it is possible to improve the cache efficiency by pre-reading the data that is expected to be accessed.

When the cache memory 4a having a small page size is used, a useless storage area can be omitted, and the rewriting of the contents of the cache memory caused by a shortage of cache pages in the case of random access can be prevented. It is possible to reduce the number of cache pages to be performed.

[0041]

As described above, according to the present invention, by switching to and selecting a storage area suitable for the contents of access to the storage area, the efficiency of reading or writing to the storage area accompanying this access is improved. 1 capable of providing a storage device capable of performing the following operations. Also,
According to the second or third aspect of the present invention, it is possible to select a storage area according to the data size by detecting the data size in random access.

Further, according to the invention according to claim 4,
By employing a cache memory as the first storage area, a storage device can be easily configured. Further, according to the invention of claim 5, the storage device can be easily configured by adopting a hard disk as the second storage area. Furthermore, according to the invention of claim 6, by switching and selecting a storage area suitable for the contents of the access to the storage area, it is possible to improve the efficiency of reading or writing to the storage area due to this access. A storage area switching method can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a memory system to which a storage device according to an embodiment of the present invention is applied.

FIG. 2 is a flowchart showing a process of selecting one of cache memories 4a and 4b.

FIG. 3 is a flowchart showing processing contents of processing executed by the memory system when an access occurs from a host computer 1;

FIG. 4 is a diagram showing a state of the cache memory when a prefetch is performed on the cache memory in the case of a sequential access.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Host computer 2 Host adapter 3 Cache controller 4 Cache memory 4a Cache memory 4b Cache memory 5 Directory area 6 Disk adapter 7 Hard disk

Claims (6)

[Claims] A plurality of storage areas having different storage capacities for storing predetermined data; access means for executing read and write access of predetermined data to the storage areas; and access from the access means. While inputting, access input determining means for determining whether the access is sequential access or random access and determining a data size corresponding to the access, and access by the access means determined while inputting by the access input determining means. A storage area determining means for determining a predetermined storage area from a plurality of storage areas in accordance with the storage area and switching to the storage area. 2. The storage device according to claim 1, wherein the access input determination means detects a data size corresponding to the random access when the access input by the access means is a random access. Storage device. 3. The storage device according to claim 2, wherein the access input determining means determines that data corresponding to the access is stored in a storage area.
The storage device, wherein the storage area determination means determines a predetermined storage area from a plurality of storage areas based on the detected data size. 4. The storage device according to claim 1, wherein said storage area is constituted by a cache memory. 5. The storage device according to claim 4, wherein the cache memory is configured so that boundaries of a plurality of storage areas can be changed. 6. When predetermined access is performed to predetermined data stored in a plurality of storage areas having different storage capacities, a storage area corresponding to the access is determined, and the determined storage area is determined. A method for determining a storage area for executing processing corresponding to an access, comprising: a plurality of storage areas having different storage capacities for storing predetermined data; and an access for reading and writing of predetermined data with respect to the storage area. An access input determining step of determining whether the access is a sequential access or a random access while inputting the access from the access step, and determining a data size corresponding to the access; and According to the access by the access step determined while the input determination step is And determines the predetermined storage area from 憶領 zone, the method for determining the storage area using the determined storage area, characterized by comprising a storage area determination step corresponding to this access.