JPH0511930A - Disk cache device - Google Patents

Abstract

PURPOSE:To surely guarantee write data. CONSTITUTION:A charging/discharging time counting means 40 counts time for charging/discharging a battery 16 to supply power to a write buffer 14. According to a charging state in the case of turning on the power supply of the battery 16, a main control means 11 decides the mode of a write operation until the cut-off of the power supply either in a write back mode to temporarily store the data in the write buffer 14 or in a write through mode to directly store the data in a magnetic disk device 15. Afterwards, the data are written in the mode decided by the main control means 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a write-back type disk cache device.

[0002]

2. Description of the Related Art Conventionally, a disk cache device has been commonly used as a means for reducing the access time of a magnetic disk device. There are two types of disk cache devices, a write-through type and a write-back type. The write-through method is effective only for the read operation. On the other hand, the write-back method is effective for both the read operation and the write operation.

In a write-back type disk cache device (hereinafter simply referred to as a disk cache device), data is temporarily held in a buffer (hereinafter referred to as a write buffer) in the device in order to speed up a write operation. The battery backs up the write buffer in preparation for power-off in the state where the write data is held in the write buffer.

FIG. 2 is a block diagram of an example of a conventional disk cache device. In this figure, a disk cache device 21 is connected to the host computer 2.
The disk cache device 21 includes a main control unit 11, a transfer control unit 12, a cache memory 13, a write buffer 14, a magnetic disk device 15, and a battery 16.
And a backup control unit 17. Main control means 1
1 controls the entire disk cache device 21. The transfer control unit 12 controls the transfer of data between the cache memory 13 and the main storage device 3 or the magnetic disk device 15.

The cache memory 13 is composed of a RAM (random access memory) or the like, and holds read data from the magnetic disk device 15. Write buffer 1
Reference numeral 4 is composed of a RAM (random access memory) or the like, and temporarily holds write data. Magnetic disk drive 1
5 finally stores the data processed by the host computer 2. The battery 16 backs up the write buffer 14. The backup control unit 17 controls the backup of the write buffer 14 by the battery 16. The host computer 2 makes a data read / write request to the disk cache device 21.

FIG. 3 is a circuit diagram showing a configuration example of a conventional backup control unit. The normal power output of the disk cache device 21 is input to the input terminal 31. While the normal power output is on, the resistors 32 and 33 and the transistors 34 and 35 output the normal power output to the collector of the transistor 35. As a result, the resistance 36
Through, the battery 16 which is a secondary battery is charged.
The collector output of the transistor 35 is the output terminal 3
It is connected to the write buffer 14 through 7. As a result, the power is supplied to the write buffer 14. The + output of the battery 16 is connected to the comparator 38. The output of the comparator 38 is connected to the main control means 11 through the output terminal 39.

Next, the operation of the conventional disk cache device will be described with reference to FIGS. However, since the read operation is not directly related to the present invention and is a known technique, it is omitted here and only the write operation and the backup operation will be described.

First, a write operation is instructed from the host computer 2 to the disk cache device 21. Then, the main control means 11 in the disk cache device 21
Uses the transfer control unit 12 to read data from the main storage device 3 in the host computer 2 and once write data to the write buffer 1
Store in 4. When all the data is stored in the write buffer 14, the write operation end notification is sent to the host computer 2. After that, write buffer 1 at an appropriate time
The data in 4 is written back to the magnetic disk device 15. While the disk cache device 21 is powered on, the normal power output is output to the collector of the transistor 35 by the operation of the resistors 32 and 33 and the transistor 34. As a result, power is supplied to the write buffer 14 through the output terminal 37. The normal power output also charges the battery 16, which is a secondary battery, through the resistor 36.

When the power supply of the disk cache device 21 is turned off in this state, the normal power supply output is turned off. Therefore, the operation of the resistors 32 and 33 and the transistor 34 turns off the transistor 35, and the normal power output and the collector of the transistor 35 are electrically disconnected. As a result, the battery 16 starts discharging and supplies power to the write buffer 14 through the resistor 36 and the output terminal 37.
As a result, the write buffer 14 is backed up by the battery while the disk cache device 21 is powered off, and the data in the write buffer 14 is retained.

The disk cache device 21 guarantees the minimum time T0 required to consume power to the lowest voltage Va that can guarantee the data in the write buffer 14 when the battery 16 is sufficiently charged. Then, when the power of the disk cache device 21 is turned on again, the voltage of the battery 16 is checked by the comparator 38. Battery 1
If the voltage of 6 is lower than the minimum voltage Va, the data in the write buffer 14 cannot be guaranteed. Therefore, the comparator 38
Outputs an alarm to the main control means 11 through the output terminal 39. In response to this, the main control means 11
An alarm is notified to the host computer 2.

[0011]

However, the above-mentioned conventional technique has the following problems. That is, in the disk cache device configured as described above, depending on the usage status of the device, the usage time (charging time) of the device
It may occur that the unused time (discharge time) is longer. In such a case, the battery is discharged without being sufficiently charged. For this reason, the data could not be guaranteed during the time T0, which is the specified value when fully charged. As a result, despite turning on the power again within time T0,
There was a problem that a battery alarm occurred and the data might be destroyed. The present invention has been made paying attention to the above points, and guarantees a certain minimum time data under any use condition,
It is an object of the present invention to provide a disk cache device that notifies a user of the charge state of a battery.

[0012]

DISCLOSURE OF THE INVENTION A disk cache device of the present invention comprises a cache memory for transferring a part of data stored in the disk device, and a write buffer for temporarily storing data to be written in the disk device. , Charging / discharging time counting means for counting the charging / discharging time of the battery that supplies power to the write buffer, and the write operation mode until the power is turned off depending on the charging state when the battery is powered on. It is characterized in that it is provided with a control means for deciding and writing to either a write-back mode for storing in a buffer or a write-through mode for directly storing in the disk device.

[0013]

In the disk cache device of the present invention,
The charging / discharging time counting means counts the charging / discharging time of the battery that supplies power to the write buffer. Then, depending on the charge state of the battery when the battery is turned on, the control unit sets the write operation mode until the power is turned off to the write-back mode in which data is temporarily stored in the write buffer or the write-through mode in which the data is directly stored in the disk device. One of the modes is decided. Then, the data is written in the mode determined by the control means.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a disk cache device of the present invention. In FIG. 1, a host computer 2, a main control unit 11, a transfer control unit 12, a cache memory 13, a write buffer 14, a magnetic disk device 1
5 and the battery 16 perform the same function as that shown in FIG. That is, the main control means 11 controls the entire disk cache device 21. The transfer control unit 12 controls the transfer of data between the cache memory 13 and the main storage device 3 or the magnetic disk device 15.

The cache memory 13 is composed of a RAM (random access memory) or the like and holds read data. The write buffer 14 is composed of a RAM (random access memory) or the like, and temporarily holds write data. The magnetic disk device 15 finally stores the data processed by the host computer 2. An optical disk device or the like may be used instead of the magnetic disk device 15. The battery 16 backs up the write buffer 14.
The host computer 2 makes a data read / write request to the disk cache device 21. The display unit 18 is a display unit that displays the state of charge of the battery according to a command from the main control unit.

The backup control unit 19 includes a battery 16
The backup of the write buffer 14 is controlled by. FIG. 4 is a diagram showing an example of the configuration of the backup control unit according to the present invention. In FIG. 4, parts having the same functions as those in FIG. 3 are designated by the same reference numerals. That is,
The normal power output of the disk cache device 21 is input to the input terminal 31. While the normal power output is on, the resistors 32 and 33 and the transistors 34 and 35 output the normal power output to the collector of the transistor 35. As a result, the battery 16, which is a secondary battery, is charged through the resistor 36.

The collector output of the transistor 35 is connected to the write buffer 14 through the output terminal 37. As a result, the power is supplied to the write buffer 14. The + output of the battery 16 is connected to the comparator 38. The output of the comparator 38 is the output terminal 3
It is connected to the main control means 11 through 9. The charge / discharge time counting means 40 is a counter that counts the charge / discharge time of the battery 16 (on / off time of the input terminal 31),
VBB is supplied as electric power.

The operation of the charge / discharge time counting means 40 is as follows. FIG. 5 is a time chart of an operation example of the charge / discharge time counting means. An input terminal 31 is connected to the control pin U / D. The charge / discharge time counting means 40 is
While + 5V is being input from the input terminal 31, it counts up at the rising edge of the clock input. A clock having an appropriate frequency is input to the clock input to divide the system clock and count the charge / discharge time. That is,
Until time t1, the device is not powered on and the battery 16 is not sufficiently charged, so the count value of the charging / discharging time counting means 40 is "0". Time point t1
From + to t2, + 5V is input from the input terminal 31,
The count value of the charge / discharge time counting means 40 is counted up to "5".

However, from time t2 to t3, the input of the input terminal 31 becomes 0V, and the charge / discharge time counting means 40
The count value of is counted down. Then, from time t3 to time t5, the input of the input terminal 31 becomes +5 V, and the count value of the charge / discharge time counting means 40 is counted up. After that, similarly, the input of the input terminal 31 becomes 0.
While V, the count value of the charge / discharge time counting means 40 is counted down (time points t5 to t6), and while the input of the input terminal 31 is +5 V, the count value of the charge / discharge time counting means 40 is counted up ( After time t6).

As a result of counting by the charging / discharging time counting means 40, an alarm is notified to the main control means 11 through the output terminal 41 during a period when the charging time for guaranteeing the data guarantee time T1 is insufficient. That is, the count value "5" corresponds to the minimum data guarantee time T1, and during this period, the write buffer 14
The data can be surely guaranteed. Therefore, when the count value of the charging / discharging time counting means 40 is equal to or less than "5", the alarm B is output (until the time point t2 and the time points t2 to t.
4 and around time t6). Also, the count value "8" is
This corresponds to the charge saturation time of the battery 16. Therefore, the count value is prevented from counting up beyond "8" (near time t5).

The charging / discharging time counting means 40 can be easily realized by using an IC such as 74LS168. The operation of the following first to fourth embodiments will be described with reference to FIGS. 1, 4, and 5.

(First Embodiment) When the power supply of the disk cache device is turned on, the output voltage of the battery 16 is checked by the comparator 38. When the output voltage of the battery 16 is equal to or lower than the lowest voltage Va that can guarantee the data, the comparator 38 outputs the alarm A as in the conventional case. As a result, the main control unit 11 knows that the data in the write buffer 14 cannot be guaranteed, and notifies the host computer 2 of the alarm. If the output voltage of the battery 16 is higher than the minimum voltage Va, but the charge amount is insufficient to guarantee the data guarantee time T1, and the disk cache device 1 is powered off in this state, the minimum data retention as a device is held. There is a possibility that the data in the write buffer 14 cannot be held during the time T1. Therefore, the charging / discharging time counting means 40 outputs the alarm B.

As a result, the main control means 11 writes all the data in the write buffer 14 to the magnetic disk device 15. Then, after that, the write data is directly written to the magnetic disk device 15 without passing through the write buffer 14 until the power of the disk cache device 1 is turned off. That is, writing is performed in the write through mode. When the output voltage of the battery is higher than the minimum voltage Va and the charge amount is sufficient to guarantee the data guarantee time T1, even if the disk cache device 1 is powered off in this state,
The data in the write buffer 14 can be held during the minimum data holding time T1 of the device. Therefore,
Neither alarm A nor B is output. As a result, the main control unit 11 operates in the write-back mode in which the write data is temporarily stored in the write buffer 14 until the power supply to the disk cache device is turned off.

(Second Embodiment) When the output voltage of the battery 16 of the first embodiment is higher than the minimum voltage Va but the charge amount is insufficient, the battery is operating in the write-through mode when the power is turned on. During operation in this write-through mode, the main control means 11 periodically detects the output terminal 41. As a result, when the charge amount becomes sufficient to guarantee the minimum data guarantee time T1, control is performed so as to shift to the original write-back mode.

(Third Embodiment) In addition to the first or second embodiment, during operation, the main control means 11 has an input terminal 31.
Is displayed on the display unit 18 to notify the user of the current charging status.

(Fourth Embodiment) In addition to the first or second embodiment, when the power supply of the disk cache device 1 is cut off, the main control means 11 is supplied from a power supply (not shown) prior to turning off the normal power supply output. A power-off signal (not shown) is output. With this power-off signal, the main control means 11 causes the display means 18 to display the state of the output terminal 41 until the normal power supply output is turned off. This gives the user a warning when the charge amount is insufficient.

[0027]

As described above, according to the disk cache device of the present invention, the charging / discharging time counting means for counting the charging / discharging time of the battery is provided, and the charging amount of the battery is insufficient when the power is turned on. Since the write operation until the power is cut off is directly written to the magnetic disk device without passing through the write buffer, the data in the disk cache device is kept for a certain period of time T1 or more under any usage condition. Can be guaranteed.
Further, as described above, even when the power is turned on to operate in the write-through mode, by periodically detecting the charge amount of the battery, when the charge amount reaches the specified value, thereafter, By controlling to operate in the original write-back mode, it is possible to improve the performance of the disk cache device in addition to the above-mentioned effects. In addition, by displaying the charging state of the battery during operation of the device, the user can operate the power supply at the discretion of the user. This makes it possible to guarantee data and always operate in the write-back mode. Furthermore, by displaying the charge state of the battery only when the power is off, the user can be alerted.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a disk cache device of the present invention.

FIG. 2 is a block diagram of an example of a conventional disk cache device.

FIG. 3 is a circuit diagram showing a configuration example of a conventional backup control unit.

FIG. 4 is a circuit diagram showing a configuration example of a backup control unit according to the present invention.

FIG. 5 is a time chart showing an operation example of a charge / discharge time counting means.

[Explanation of symbols]

1 Disk cache device 2 Host computer 11 Main control means 12 Transfer control unit 13 cache memory 14 write buffer 15 Magnetic disk unit 18 display means 19 Backup control unit 40 Charge / discharge time counting means

─────────────────────────────────────────────────── ───Continued from the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G06F 3/06 304 Z 7165-5B

Claims (4)

[Claims] 1. A cache memory for transferring a part of data stored in a disk device, a write buffer for temporarily storing data to be written in the disk device, and a battery for supplying power to the write buffer. A charge / discharge time counting means for counting the discharge time, and a write operation mode until the power is turned off, depending on the charge state at the time of power-on of the battery, a write-back mode in which data is temporarily stored in a write buffer, or the disk directly. A disk cache device, comprising: a control means for deciding and writing to either a write through mode to be stored in the device. 2. The control means, when in the write-through mode, periodically detects the state of charge, and controls to shift to the write-back mode when the battery is sufficiently charged. The disk cache device according to claim 1. 3. The disk cache device according to claim 1, further comprising display means for displaying a charge state of the battery during operation of the device. 4. The disk cache device according to claim 3, wherein the display means displays the charge state of the battery only when the power is turned off.