JPH06309232A - Control system for disk cache - Google Patents

Abstract

PURPOSE:To protect data in the disk cache memory and prevent a computer system from malfunctioning. CONSTITUTION:The computer system which is equipped with the uninterruptive power unit equipped with a storage battery 1 and a means 2 for detecting the remaining capacity of the storage battery 1, a voltage setting means, the disk cache memory 7, an external storage device 8, and a disk cache controller 4 which controls the disk cache memory 7 and external storage device 8 and caches data on a disk controls the disk caching by comparing the remaining capacity of the storage battery 1 detected by the remaining capacity detecting means 2 with a voltage set value set by the voltage value setting means and then selecting a copy-back system or write-through system for the disk cache control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data protection system for a disk cache memory in a computer system using an uninterruptible power supply.

[0002]

2. Description of the Related Art A disk cache is located between a main memory and an external storage device, and in data transfer with the external storage device, the time for inputting / outputting data to / from the external storage device (hereinafter abbreviated as access time) is set. Provided for speed. Generally, the external storage device is composed of a magnetic disk such as a hard disk drive or a floppy disk drive. And the access time of them is about 10 to 3 compared with the main memory composed of the semiconductor memory.
0 times slower. Therefore, for example, as a means for apparently shortening the data access time to the external storage device, there is a method of placing a disk cache memory composed of a semiconductor memory between the main memory and the external storage device.

As an operation of the disk cache memory,
For example, the data input / output from the external storage device is written in the disk cache memory. Then, while the data is held in the disk cache memory, the data can be input / output from the disk cache memory (this is called a disk cache hit). Then, as long as the data is held in the disk cache, it is not necessary to read the data from the external storage device. In this case, data can be input / output from / to the disk cache memory that has a faster access time than the external storage device, and therefore the data access time to the external storage device is apparently faster.

There are two types of disk cache, one realized by hardware and the other realized by software.
There are types. Hardware disk cache
The disk cache memory and the disk cache control device are integrated. And, it is placed between the external storage device and the main memory. Further, the software disk cache allocates a part of the main memory to the disk cache memory, and the disk driver of the operating system performs the disk cache operation.

Here, the unit price of the disk cache memory is higher than that of the external storage device. Therefore, the storage capacity of the disk cache memory incorporated in the computer system is much smaller than the storage capacity of the external storage device. Then, all the data accessed from the external storage device cannot be written in the disk cache memory having a small storage capacity. for that reason,
If there is no area to write data in the disk cache memory, it is necessary to make a free area in the disk cache memory. The empty area is created by invalidating the data in the disk cache memory or by flushing the data to an external storage device. Then, the data that could not be written into the empty area is written.

By the way, there are two types of methods for writing the data held in the disk cache memory to the memory (hereinafter referred to as a write algorithm), a write-through method and a copy-back method. The write-through method is a method in which an operation of writing data from a main memory to an external storage device for a certain memory address is immediately executed to the external storage device. That is, the data written in the disk cache memory is simultaneously written in the external storage device. Therefore, the data corresponding to a certain memory address always matches between the disk cache memory and the external storage device. On the other hand, in the copy back method, the data write operation from the main memory is performed only to the disk cache memory. The data corresponding to a certain memory address may differ between the disk cache memory and the external storage device. In this case, update data exists in the disk cache memory and old data exists in the external storage device. These two types of methods are disclosed in JP-A-4-123151.

Here, of the above-mentioned two types of write algorithms, the copy-back method, in which data is not immediately written to the external storage device, has a faster data access time. Further, since the disk cache memory is a volatile memory, data in the disk cache memory will be lost during a power failure. Therefore, since the latest update data is held in the disk cache memory in the copy-back method, the update data is lost at the time of power failure, causing a malfunction of the computer due to an error in the data content. Therefore, the update data of the disk cache memory is lost at the time of power failure, etc., and the copy back method cannot prevent the malfunction of the computer system due to the loss of data.

On the other hand, in the write-through method of always accessing the external storage device when writing data from the main memory, the data access time is not faster than that of the copy-back method. Further, the write-through type write algorithm always holds the same update data as the disk cache memory in the external storage device. for that reason,
Even if the update data in the disk cache memory, which is volatile memory, is lost during a power failure, the same update data as the disk cache memory is held in the external storage device, which is non-volatile memory. It does not cause the malfunction of. There is a method disclosed in Japanese Patent Laid-Open No. 3-263146 as a method that can protect the data in the disk cache memory even in the case of a power failure by using a copy back method in which the data access time is fast.

As described above, there is an uninterruptible power supply device as a device for preventing malfunction of a computer system caused by a power failure. The uninterruptible power supply is connected between the computer system and the commercial power supply, and when a power failure such as a power failure, momentary voltage drop, or power instability occurs, the commercial power is immediately replaced with the rechargeable battery of the uninterruptible power supply. As a result, power is supplied to the computer system to prevent malfunction of the computer system. In this case, the function of the uninterruptible power supply automatically transmits a power failure message to a computer system using the uninterruptible power supply when a power failure occurs through a signal cable such as RS232C. After that, unless the commercial power is restored, the uninterruptible power supply transmits a shutdown message not to supply power to the computer system. Then, the uninterruptible power supply stops supplying power to the computer system. Here, the user using the computer system saves the necessary data in the external storage device after receiving the power failure message and before receiving the shutdown message to shut off the power from the uninterruptible power supply. You will be prepared. The uninterruptible power supply is disclosed in JP-A-2-228223 and the like.

[0010]

As described in the prior art, the data of the disk cache memory has a problem that the content of the data is lost unless power is supplied. Therefore, even when a power failure occurs, the power of the computer system is replaced with the rechargeable battery of the uninterruptible power supply to supply the power to the computer system. Then, the loss of the data in the disk cache memory due to a power failure or the like was prevented. However, the uninterruptible power supply cannot supply power to the computer system, for example, immediately after the charging of the uninterruptible power supply is started or when a power failure occurs when the rechargeable battery of the uninterruptible power supply is significantly reduced. As a result, the data in the disk cache memory of the computer system will be lost. At this time, if the disk cache control is performed by the copy back method, the updated latest data will be lost. Then, the computer system may malfunction due to data error. Therefore, it is an object of the present invention to grasp the remaining amount of the rechargeable battery of the uninterruptible power supply and eliminate the malfunction of the computer system due to the error of the update data even if the update data of the disk cache memory is lost due to the power failure.

[0011]

In order to solve the above problems, a remaining capacity detector is provided as a means for detecting the remaining capacity of the rechargeable battery of the uninterruptible power supply. A means for determining whether or not the uninterruptible power supply can supply power to the computer system at the time of a power failure is provided based on the detected remaining capacity of the rechargeable battery. Here, a set value circuit for setting a value to be compared with the remaining capacity for making a determination is provided. The value set by the set value circuit is called a set value. Further, a disk cache control system selection circuit is provided which sends the result of comparing the set value and the value of the remaining capacity to the disk cache controller by a signal. When the value of the remaining capacity of the rechargeable battery is smaller than the set value, the disk cache control method selection circuit outputs a signal to the disk cache controller to perform disk cache control by the write through method. When the disk cache control is performed by the write-through method, the data in the disk cache memory corresponding to a certain memory address becomes the same as the data in the external storage device. Therefore, regardless of the remaining capacity of the rechargeable battery of the uninterruptible power supply, even if the data of the disk cache memory is lost at the time of power failure, the same data exists in the external storage device, and the computer malfunctions due to data error. It can be prevented. If the value of the remaining capacity of the rechargeable battery is larger than the set value, the disk cache control system selection circuit outputs a signal to the disk cache controller to perform the disk cache control by the copy back system. If the disk cache control is performed by the copy-back method, the data can be accessed between the main memory and the external storage device faster than the write-through method.

[0012]

As described above, the remaining capacity of the rechargeable battery is detected by the remaining capacity detecting means. Then, the disk cache control system selection circuit reads the remaining capacity of the rechargeable battery by the detection signal. When the value of the remaining capacity is larger than the set value, it is considered that the uninterruptible power supply operates to supply sufficient power to the computer system when a power failure occurs. Therefore, even if a power failure occurs, the data in the disk cache memory will not be lost. Therefore, the disk cache control system selection circuit sends a signal for performing the disk cache control by the copy back method to the disk cache controller. Then, the disk cache controller controls the disk cache by the copy-back method and operates the computer system at high speed.

On the other hand, when the value of the remaining capacity is smaller than the set value, there is a possibility that the uninterruptible power supply cannot sufficiently supply power to the computer system against a power failure. Therefore, when a power failure occurs, the data in the disk cache memory may be lost. Therefore, the disk cache control system selection circuit sends a signal for performing disk cache control by the write through system to the disk cache controller. Then, the disk cache controller controls the disk cache by the write-through method. When the disk cache control is performed by the write-through method, the data written in the disk cache memory is also written in the external storage device. Here, if the remaining amount of the rechargeable battery of the uninterruptible power supply is not sufficient, power cannot be supplied to the computer system.
Therefore, the data in the disk cache memory is lost. However, if the disk cache control is performed by the write-through method, even if the data in the disk cache memory is lost due to a power failure, it is sufficient to refer to the data from the external storage device and malfunction of the computer system due to incorrect data. Can be prevented.

As described above, the disk cache control system selection circuit protects the data in the disk cache memory by grasping the remaining capacity of the rechargeable battery of the uninterruptible power supply and selecting the disk cache control system of the computer system. The computer system to operate without malfunction.

[0015]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows an example of a block diagram of an entire system incorporating a disk cache control system selection circuit of the present invention. 1 is a rechargeable battery for the uninterruptible power supply, 2
Is a remaining capacity detection circuit (remaining capacity detection means) of the rechargeable battery 1 for detecting the remaining capacity of the rechargeable battery 1 of the uninterruptible power supply, 3 is a disk cache control system selection circuit for selecting the disk cache control method of the computer system Reference numeral 4 is a disk cache controller for controlling the disk cache memory 7, 5 is a CPU of the computer system, 6 is a main memory of the computer system, 7 is a disk cache memory for caching data in the external storage device 8, and 8 is a nonvolatile memory for storing data. Is an external storage device such as a hard disk, 9 is a detection signal from the remaining capacity detector 2, and 10 is a signal sent from the disk cache control system selection circuit 3 for determining the disk cache control system.

FIG. 2 shows an internal view of the disk cache control system selection circuit 3 shown in FIG. 1, and 12 is a set value circuit for determining a set value for switching the disk cache control system. Then, these set value circuits 12 are configured by a dip switch or the like. Also,
In terms of software, the set value can be determined by sending a signal of the set value determined by the computer system to the set value circuit 12 as an internal signal to the disk cache control selection circuit 3.
The signal 13 is a signal of the set value determined by the set value circuit 12. Reference numeral 14 is a comparator for comparing the remaining capacity detection signal 9 and the set value signal 13. The comparator 14 determines the optimum disk cache control method at that time. Then, the determined disk cache control method is sent to the computer system as a signal 10.

The operation of the disk cache control system selection circuit 3 shown in FIGS. 1 and 2 will be described with reference to the flow chart of FIG.

The setting value for switching between the write-through method and the copy-back method is determined by the user of the system using the setting value circuit 12. (Step). The remaining capacity of the rechargeable battery 1 is determined by the remaining capacity detector 2 by measuring the voltage of the rechargeable battery 1 and the like. Then, the remaining capacity detector 2 sends the remaining capacity of the rechargeable battery 1 to the disk cache controller (step). Then, the disk cache control system selection circuit 3 compares the remaining capacity of the rechargeable battery 1 with the set value by the comparator 14 (step).

If the value of the remaining capacity is larger than the set value, the disk cache control system selection circuit 3 outputs the signal 1
The voltage value of 0 is asserted to the Hi level and sent to the disk cache controller 4 (step). The disk cache controller 4, which has received the Hi-level signal, checks whether the signal 10 has changed from the Low level to the Hi level (step). If the signal 10 has not changed from the Low level to the Hi level, it is determined that the computer system is performing the disk cache control by the copy back method, and the process returns to the step. On the other hand, if the signal 10 changes from the Low level to the Hi level, it is determined that the computer system is performing the disk cache control by the write-through method, and the disk cache controller 4 performs the operation of switching the disk cache control to the copyback method. (Step). The disk cache controller 4 performs disk cache control by the copy back method, so that the computer system operates at high speed (step).

When the value of the remaining capacity is smaller than the set value, the disk cache control system selection circuit 3 outputs the signal 1
The voltage value of 0 is asserted to the low level and sent to the disk cache controller 4 (step). Lo
The disk cache controller 4 which has received the signal of the w level, when receiving the signal 10, changes the signal 10 to Hi.
Check whether the level has changed to the Low level (step). If the signal 10 has not changed from the Hi level to the Low level, it is determined that the computer system is performing the disk cache control by the write-through method, and the process returns to the step. On the other hand, if the signal 10 changes from the Hi level to the Low level, it is determined that the computer system is performing the disk cache control by the copy back method, and the disk cache controller 4 performs the operation of switching the disk cache control to the write through method. . In this case, since the update data is written in the disk cache memory 7, the disk cache controller 4 performs the operation of writing the update data in the disk cache memory 7 into the external storage device 8. This operation is called flushing the disk cache memory 7 (step A). After flushing the disk cache memory 7, the disk cache controller 4 performs disk cache control by the write-through method. By performing the disk cache control by the write-through method, the data in the disk cache memory 7 and the data in the external storage device 8 become equal.
At this time, even if the power of the disk cache memory 7 is lost due to a power failure due to a power failure or the like, the same data as the lost data is stored in the external storage device 8. You can read from 8. Therefore, it is possible to prevent malfunction of the computer system due to data error. (Step B).

Here, switching of the disk cache control method depending on the remaining capacity of the rechargeable battery 1 will be described with reference to FIG. FIG. 4 shows how the remaining capacity of the rechargeable battery 1 increases with time. Then, the change of the signal 10 with respect to the remaining capacity of the rechargeable battery 1 and the set value and the switching of the disk cache control method are shown. The set value circuit 12 sets the set value to X% of the full remaining capacity of the rechargeable battery 1. The remaining capacity detector 2 detects the remaining capacity of the rechargeable battery 1, and sends a detection signal 9 to the disk cache control selection circuit 3. The disk cache control method selection circuit 3 has a remaining capacity of X%.
If smaller, Lo to disk cache controller
The w signal 10 is transmitted. Then, the disk cache controller 4 of the computer system that receives the Low signal 10 performs the disk cache by the write-through method. If the remaining capacity is X% or more, the disk cache control selection circuit 3 sends the Hi signal 10 to the disk cache controller. Then, the Hi signal 10
The disk cache controller 4 of the computer system that has received the command performs disk cache control by the copy back method.

Although FIG. 1 shows a computer system using disk cache control by hardware, the same applies to disk cache control by software. FIG. 5 shows an example of a computer system of disk cache control by software. In FIG. 5, the disk cache memory 7 is on the main memory 6.
The disk cache memory 7 is managed by software. Therefore, according to the signal 10 from the disk cache control system selection circuit 3, the software performs the disk cache control by either the copy back system or the write through system. Therefore, the software controls the disk cache memory 7 on the main memory 6. Therefore, the computer system using the disk cache control by software can also select the disk cache control by the signal 10 from the disk cache control selection circuit 3.

[0024]

As described above, according to the present invention, by providing the disk cache control system selection circuit for selecting the disk cache control system for the value of the remaining capacity of the rechargeable battery of the uninterruptible power supply, When the remaining capacity is small, the disk cache control is performed by the write-through method, so that the computer system can be operated without malfunction even when the update data of the disk cache memory is lost at the time of power failure. Further, when the remaining capacity is sufficient, the computer system can be operated at high speed by controlling the disk cache by the copy back method.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an entire system including the present invention.

FIG. 2 is a diagram showing an example of a disk cache control selection circuit 3 of the present invention.

FIG. 3 is a flowchart illustrating the operation of a disk cache control selection circuit 3 shown in FIGS. 1 and 2.

FIG. 4 shows how the signal 10 switches between Hi and Low depending on the change in the remaining amount of the rechargeable battery 1 when the set value is set to X% of the remaining amount, and the disk cache control is a write-through method or a copy-back method. It is the figure which showed a mode that it switched to.

FIG. 5 is a diagram of a computer system using a software disk cache.

[Explanation of symbols]

 1 ... Rechargeable battery, 2 ... Remaining amount detector, 3 ... Disk cache control selection circuit, 4 ... Disk cache controller, 5 ... CPU, 6 ... Main memory, 7 ... Disk cache memory, 8 ... External storage device, 9 ... Remaining Quantity detection signal, 10 ... Disk cache control determination signal, 12 ... Setting value circuit, 13 ... Signal indicating setting value determined by setting value circuit 12, 14 ... Comparator.

Claims (6)

[Claims] 1. An uninterruptible power supply comprising a rechargeable battery and means for detecting the remaining capacity of the rechargeable battery, and voltage value setting means.
In a computer system performing a disk cache including a disk cache memory, an external storage device, and a disk cache controller that controls the disk cache memory and the external storage device, the rechargeable battery detected by the remaining capacity detecting means A disk cache control method characterized in that the disk cache control is selected from a copy-back method and a write-through method by comparing the remaining capacity with a voltage setting value set by the voltage value setting means. 2. The disk cache control system selection circuit according to claim 1, wherein the remaining capacity detected by the remaining capacity detecting means of the rechargeable battery is compared with the voltage set value set by the voltage value setting means, and the remaining capacity is determined. When the capacity value is smaller than the voltage setting value, the disk cache control system selection circuit selects a write-through system disk cache control system, and the disk cache controller selects a write-through system by a signal from the disk cache system selection circuit. A disk cache control method, which protects data in the disk cache memory against data loss due to a power failure or the like by performing the disk cache by a through method. 3. The disk cache control system selection circuit according to claim 1, further comprising a set value circuit for determining the voltage set value for switching the disk cache control, the voltage set value and the rechargeable battery. A comparator for comparing the detection signal from the remaining capacity detecting means of the computer system, and the comparator selects the write-through method or the copy-back method for the disk cache control method of the computer system. The control method of the disk cache including a disk cache control method selection circuit, wherein the comparator sends the signal of (1) to the disk cache controller. 4. A set value circuit according to claim 3, wherein a set value circuit for setting a voltage set value by hardware or software is incorporated, and a disk cache control method selecting circuit is provided. control method. 5. A disk cache control method for a computer system according to claim 1, wherein the disk cache control method selection circuit is built in the computer system. 6. The computer system according to claim 1, wherein the disk cache control system can be selected by a signal from a disk cache control system selection circuit whether it is hardware or software. Disk cache control method.