JP2906739B2 - Storage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage device capable of restoring a stored state by holding the stored state at a certain point in time.

[0002]

2. Description of the Related Art In a conventional storage device for holding a storage state at a certain point in time and restoring the storage state, a plurality of storage means are arranged to hold the storage state at each point in time and to cope with this. (Eg, W. Hwu and Y. Patt:
“Checkpoint Repair for Hi
gh-Performance Out-of-Ord
er Execution Machines ", IE
EE Transactions on Comput
ers, Vol. C-36, No. 12, pp. 149
6-1514, Dec. 1987). In this storage device, the storage state can be restored by transferring all the storage states at a certain point in time as shown in FIG.

[0003]

However, in the above-described storage device, as the amount of storage per storage state increases, the time cost and hardware cost required for transfer increase. As described above, the conventional storage device has a problem to be solved regarding the transfer time and the hardware cost.

An object of the present invention is to provide a storage device which is excellent in efficiency by solving such a problem and avoiding redundant data transfer.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, a first invention of the present application has two alternative write modes, and when switching from one write mode to the other write mode, In a storage device that allows the storage state at the time of switching to be restored by holding the storage state at the time of switching,
A first means for writing data, two second means which are storage means to which data is written by the first means, and a method for writing data to two second means by the first means. Two third means for respectively retaining histories;
A fourth means for performing data transfer between the two second means, and a fifth means for controlling transfer to the fourth means based on a write history state of the third means, and by performing data transfer between the second means to manage a second means for each of a plurality of words, characterized by avoiding redundant data transfer between the second means.

Further, the second invention of the present application includes: a sixth means for changing a write history to the second means in addition to the first invention, whereby a redundant means between the second means is provided. Data transfer is avoided.

[0007]

By taking such means, it is possible to transfer only necessary parts when returning to the state at a certain point in time. Thereby, redundant data transfer can be avoided and an efficient storage device can be provided.

FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention. In the figure, reference numeral 10 denotes data writing means for writing data to the storage means. Numerals 21 and 22 denote storage means A and storage means B, respectively. Data is written by the data writing means 10 into both or one of 21 and 22. 31 and 32 are storage means A21,
Holding the presence or absence of writing to the storage means B22,
Write history A and write history B. 40 is storage means A
And transfer means for transferring data between the storage means B.
Reference numeral 50 denotes transfer control means for controlling the transfer means 40 based on the states of the write history A31 and the write history B32.

FIG. 2 shows the format of the write history A31 or the write history B32. Here, the storage unit A2
1 and B22 are both composed of N words, and 0
To (N-1). This address is also used in the write history A31 and the write history B32, and the address x (x = 0 to (N−
1)) is managed by the address x of the write history A31, and the address y of the storage means A22 (y = 0 to (N-1))
Is managed by the address y of the write history A32.

The operation of the storage device having the above configuration will be described. The writing of data from the data writing unit 10 is stored in the storage unit A21 or the storage unit B22. If the contents of both the storage unit A21 and the storage unit B22 are made equal at a certain point in time, the following two write modes are alternately repeated, and the storage unit A21 and the storage unit B22 are repeated.
Are alternately held at a certain point in time, it is possible to return to the held state. However, the initial contents of the write history A31 and the write history B32 are all 0.

In the first mode, in order to hold the state at the time of entering this mode in the storage means A21, writing to the storage means A21 is temporarily stopped, and writing is performed only to the storage means B22. . In the first mode, writing is performed only on the storage unit B22.
The content of the 32nd X word is set to 1 and the writing history is stored. In the first mode, the write history A
If the content of the Y-th word 31 is 1, the data of the Y-th word in the storage means A21 is transferred to the Y-th word in the storage means B22. If this transfer is successful, the content of the Y-th word in the write history A31 is set to 0. At this time, if the content of the Yth word in the write history 32 is 1, the transfer is not performed, and the content of the Yth word in the write history A31 is set to 0. This transfer is performed by the write history A31.
Until the contents of all words in the word "0" become zero, and do not switch to another mode until this is completed.

In the second mode, in order to hold the state at the time of entering this mode in the storage means B22, writing to the storage means B22 is temporarily stopped, and writing is performed only to the storage means A21. . In the second mode, writing is performed only on the storage unit A21. Therefore, for example, when writing is performed on the Xth word of the storage unit A21, the writing history A
The content of the 31st X word is set to 1 and the writing history is stored. In the second mode, the write history B
If the content of the 32nd Y word is 1, the data of the Y word of the storage means B22 is transferred to the Y word of the storage means A21. If this transfer is successful, the content of the Y-th word in the write history B32 is set to 0. At this time, if the content of the Y-th word in the write history A31 is 1, the transfer is not performed, and the content of the Y-th word in the write history B32 is set to 0. This transfer is performed by writing history B3
2 until the contents of all words are zero, and do not switch to another mode until this is done.

In the above two operation modes, the storage means A2
By using either 1 or the storage means B22 to hold the state at a certain point in the past, it is possible to return to the past state. That is, in the first mode, the state at the time of entering this mode is stored in the storage unit A21, and the storage unit B22 can be returned to this state in the following procedure. First, write history B
If the content of the Y word of 32 is 1, the data of the Y word in the storage means A21 is transferred to the Y word in the storage means B22. If this transfer is successful, the content of the Y-th word in the write history B32 is set to 0. This transfer is continued until the contents of all the words in the writing history B32 become 0. Then, write history A
If the content of the Y-th word 31 is 1, the data of the Y-th word in the storage means A21 is transferred to the Y-th word in the storage means B22. If this transfer is successful, the content of the Y-th word in the write history A31 is set to 0. This transfer is continued until the contents of all the words in the writing history A31 become 0. By this procedure, both the storage means A21 and the storage means B22 can return to the state at the time of entering this mode.

In the second mode, the state at the time of entering this mode is stored in the storage means B22, and the storage means A21 can be returned to this state by the following procedure. First, if the content of the Y-th word in the writing history A31 is 1, the data of the Y-th word in the storage means B22 is stored in the storage means A.
Transfer to the 21st Y word. If this transfer is successful, the content of the Y-th word in the write history A31 is set to 0. This transfer is continued until the contents of all the words in the writing history A31 become 0. Then, the content of the Y-th word in the writing history B32 is 1
If so, the data of the Yth word of the storage means B22 is transferred to the Yth word of the storage means A21. If this transfer is successful,
The content of the Y-th word in the write history B32 is set to 0. This transfer is continued until the contents of all the words in the writing history B32 become 0. By this procedure, the storage means A21 and the storage means B
22 can return to the state at the time of entering this mode.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 3 shows an embodiment of the storage device according to the present invention. In the figure, write history A31 and write history B3
2 except that a redundant transfer avoiding means 60 is provided between
It has the same configuration as the embodiment of FIG. 1 described above. In this configuration, the redundant transfer avoiding means 60 avoids redundant data transfer by operating the write history A31 or the write history B32 according to the state of the write history A31 and the write history B32. That is, in the first mode described above, when the contents of both the Xth word of the writing history A31 and the Xth word of the writing history B32 become 1, the content of the Xth word of the writing history A31 is set to 0. In the second mode, when the content of the X-th word of the writing history A31 and the content of the X-th word of the writing history B32 both become 1, the content of the X-th word of the writing history B32 is set to 0. Thus, redundant data transfer in the storage device described above can be avoided.

[0016]

As is apparent from the above description, according to the present invention, by performing finer control on a word-by-word basis as compared with a conventional storage device which transfers the entire storage means,
It is possible to provide an efficient storage device with less waste in time and hardware costs required for transfer and less waste.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an apparatus according to an embodiment of the first invention of the present application.

FIG. 2 is a diagram showing a configuration of a write history A or a write history B in FIG.

FIG. 3 is a configuration diagram showing an embodiment of the second invention of the present application.

FIG. 4 is a configuration diagram showing a conventional storage device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Data writing means 21, 22 Storage means 31, 32 Writing history 40 Transfer means 41 All transfer means 50 Transfer control means 60 Redundant transfer avoidance means

Claims (2)

(57) [Claims] The present invention has two alternative write modes, and when switching from one write mode to the other write mode, retains the storage state at the time of the switch, thereby storing the memory at the time of the switch. In a storage device capable of restoring a state, a first unit for writing data, two second units as storage units to which data is written by the first unit, and a first unit for writing data. Two third means for respectively holding two data writing histories to the second means, a fourth means for transferring data between the two second means, and a writing history of the third means And a fifth means for controlling the transfer of the fourth means according to the state of the second means, and further controlling the second means for each of a plurality of words to perform data transfer between the second means. , Redundant data transfer between the second means Storage device, which avoids the problem. 2. The apparatus according to claim 1, further comprising a sixth means for changing a write history to said second means, thereby avoiding redundant data transfer between said second means.
A storage device according to claim 1.