JPH05250190A - Cache device - Google Patents

Abstract

PURPOSE:To provide a cache device capable of promptly realizing the original operation of a cache device when a backup abnormality occurs in a state that data does not exist in a write buffer. CONSTITUTION:A flag F showing whether data to be written in a magnetic disk device 105 is stored in a write buffer 104 or not or a data parameter DP is set on a nonvolatile memory 108. When a backup abnormality occurs, the flag F or the data parameter DP is referred to. When the fact that data is not stored in the write buffer 104 is confirmed, the initialization of the write buffer 104 is automatically enforced. The report that the initialization of the write buffer 104 was automatically enforced in accordance with the backup abnormality for a host computer 2 is enforced only when the command from the host compute 2 is received.

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 cache device.

[0002]

2. Description of the Related Art A cache device is generally used as a device for shortening the access time of a storage device which is difficult to access at high speed due to a mechanical operation such as a magnetic disk device. There are two types of cache devices, a write-through system that is effective only for data read (read) operation from a magnetic disk and a write-back system that is effective for both data read (read) and data write (write) operations. is there. Here, the write-back type cache device will be taken as an example.

In a write-back type cache device,
In order to speed up the write operation, the data to be the write operation is temporarily stored in the buffer (write buffer). When writing to the write buffer is completed, the host device that performs writing is immediately released and other operations are performed without being restricted by the mechanical operating time required to access the magnetic disk device. can do.

FIG. 2 shows a conceptual diagram of a conventional cache device. The cache device 1 shown in FIG.
A transfer control unit 102, a cache memory 103, a write buffer 104, a magnetic disk device 105, a battery 106, and a backup control unit 107 are provided.

The main control unit 101 is composed of a processor and the like for controlling the operation of the entire cache device 1 and for controlling the input / output of commands and the like executed with the host computer (upper device) 2. The transfer control unit 102 includes a host computer 2, a magnetic disk device 105, and a cache memory 10.
3, and a processor or the like for controlling data transfer between the write buffers 104.

The cache memory 103 is composed of a RAM or the like for storing data (read data) read from the magnetic disk device 105. Write buffer 10
4 is composed of a RAM or the like for storing data (write data) to be written in the magnetic disk device 105.

The magnetic disk device 105 is composed of a hard disk device or the like for permanently storing data. The battery 106 is composed of a rechargeable storage battery or the like that supplies electric power to the light buffer 104. The backup control unit 107 controls charging / discharging of the battery 106 and detects a backup abnormality of the write buffer 104 due to a voltage drop of the battery 106.

Here, the backup controller 107 will be described in detail with reference to FIG. FIG. 3 is a circuit diagram of the backup control unit 107. When the power of the cache device 1 is turned on, the voltage (VC) 201 is the backup control unit 10
Applied to 7. This voltage 201 is applied to resistors 202 and 203
Of the transistor 204 (N
It is applied as a (PN type) base voltage. The voltage 201 is applied to the emitter of the transistor 205 (PNP type).

Base of transistor 205 and transistor
Since the collector of 204 is connected, transistor 20
Along with the shift of 4 to the on state, the transistor 205 also shifts to the on state, and the backup voltage (VBB) 207 based on the collector voltage of the transistor 205 is output. The backup voltage 207 is applied to the battery 106 via the resistor 206.
Applied to charge the battery 106. In addition, the voltage 201
If is cut off, the battery 106 starts discharging and the backup voltage 207 is continuously output via the resistor 206.

On the other hand, the voltage applied to the battery 106 is
The comparator 208 compares it with a preset reference voltage (Va) and outputs a comparison result (alarm) 209 to the main controller 101. The comparison result 209 is, for example, binary data that is valid when the voltage is equal to or lower than the reference voltage (Va) and is invalid when the voltage exceeds the reference voltage. In addition,
During discharging of the battery 106, the comparator 208 calculates the comparison result 209 based on the output voltage of the battery 106.

Now, returning to FIG. 2, the write operation in the conventional cache device will be described. When the write operation is executed from the host computer 2 to the cache device 1, the main control unit 101 drives the transfer control unit 102 to read the data from the main storage device (not shown) on the host computer, and to the write buffer 104. Remember. Write buffer 10
When all the data instructed by the host computer 2 is stored in 4, the main control unit 101 sends a write operation end notification to the host computer 2.

The main control unit 101 drives the transfer control unit 102 at a preset predetermined time, for example, when the cache device 1 is not accessed for a certain period of time or when a preset cycle arrives, and the write buffer 104 is driven. The data is read from and written in the magnetic disk device 105.

The write buffer 104 has a magnetic disk.
If the power supply is cut off while the data to be written to 105 is stored, the transistor 20 of the backup control unit 107
5 is turned off, the voltage 201 and the collector of the transistor 205 are electrically disconnected, and the discharge of the battery 106 is started. This results in a voltage 207 based on the power of battery 106.
Is continuously supplied, and the write buffer 104 is backed up and the stored contents are saved.

Now, with reference to FIGS. 4 and 5, a conventional cache device startup process will be described. FIG. 4 is a first flowchart of a conventional startup process. When the power of the cache device 1 is turned on, the main control unit 101 changes the comparator of the backup control unit 107.
The comparison result 209 output by the 208 is recognized (step S
1), indicating whether it is valid or invalid, that is, battery
It is determined whether the output voltage of 106 is less than or equal to the reference voltage (Va) (step S2).

If the result of the determination in step S2 is invalid, that is, if it exceeds the reference voltage, a data check such as parity check or ECC is performed to confirm that the data in the write buffer 104 is not destroyed. Then, the presence or absence of an error is determined (step S3). If the result of step S4 is normal, it is determined that the backup of the write buffer 104 is normal (step S5), and the process ends.

If the result of the determination in step S2 is valid, that is, if it is less than or equal to the reference voltage, and if an error is determined in step S4, it is determined that the backup is abnormal (step S6), and the main control unit 101 is also present. Abnormality occurrence information indicating the occurrence of a backup abnormality is stored in the upper register or the like (step S7), and the process ends.

The operation when the cache device 1 receives a command from the host computer 2 after the processing of FIG. 4 is executed will be described with reference to FIG. Figure 5
It is the 2nd flow chart concerning the conventional starting processing. The figure shows the processing when the cache device 1 first receives a command from the host computer 2 after determining the presence / absence of a backup abnormality. The main control unit 101 first indicates the occurrence of a backup abnormality. It is determined whether or not the abnormality occurrence information is stored (step S11). Step S
As a result of 11, if the memory exists, the write buffer 104
It is determined whether or not a command for initializing is received (step S12).

When the result of step S12 is NO, that is, when a command other than initialization of the write buffer 104 is received, the main control unit 101 reports to the host computer 2 that a backup abnormality has occurred (step S13). , The memory of the backup abnormality is erased (step S14), and the process ends. The host computer 2 side that has received the report of the backup abnormality outputs an initialization command instructing the initialization of the write buffer 104.

If there is no memory as a result of step S11, and if the result of step S12 is YES, the command received from the host computer 2 is executed (step S11).
15), the process ends.

[0020]

In the past, if data was present in the write buffer 104 when a backup error occurred, the data originally stored in the magnetic disk device 105 after the write buffer 104 was initialized. Is required to be written again (recovery process). Further, when there is no data in the write buffer 104, the recovery process is unnecessary, and only the initialization of the write buffer 104 needs to be executed.

However, since the conventional cache device 1 only detects whether or not a backup abnormality has occurred, the contents of the magnetic disk device 105 must be read after the write buffer 104 is initialized. It is necessary to check the presence or absence of unstored data and determine whether or not to carry out the recovery process. It is very important to immediately set the cache device 1 to the normal operating state when a backup error occurs. It was difficult for me.

The present invention has been made by paying attention to the above points, and when a backup abnormality occurs in a state where there is no data in the write buffer, the cache device which can quickly realize the original operation of the cache device. The purpose is to provide.

[0023]

According to a first aspect of the present invention, a write buffer for temporarily storing data to be written to a storage device, a battery for backing up the write buffer, and an abnormality of the backup are detected. A backup control unit, a non-volatile memory that stores a flag indicating that the data has been stored in the write buffer, and refers to the flag when the abnormality is detected,
The present invention relates to a cache device having initialization control means for initializing the write buffer when the flag indicates that the data has not been stored. According to a second aspect of the present invention, a response control means for reporting the fact that the initialization has been carried out to the host device when the access by the host device is accepted after the initialization and the abnormality of the backup is detected. The present invention relates to a cache device including and. According to a third aspect of the present invention, a write buffer for temporarily storing data to be written to a storage device, a battery for backing up the write buffer, and a data parameter indicating a data amount of the data stored in the write buffer. A non-volatile memory for storing the data, a backup control unit for detecting an abnormality of the backup, and when the abnormality is detected, the data parameter is calculated based on the data stored in the write buffer, and the non-volatile When the comparison result for comparing with the data parameter stored in the memory does not match the comparison result and the data parameter stored in the non-volatile memory indicates that no data is stored, the write buffer is initialized. The present invention relates to a cache device having initialization control means for performing the above.

[0024]

This device sets a flag or a data parameter, which indicates whether or not the write buffer stores data that can be written to the storage device, in the nonvolatile memory.
When a backup error occurs, the flag or data parameter is referred to, and if it is confirmed that the data is not stored in the write buffer, the write buffer is automatically initialized. Also, the report that the write buffer has been automatically initialized due to the backup abnormality to the host device is performed only when the command is received from the host device.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a conceptual diagram of a cache device of the present invention. The cache device 11 shown in the figure has a main controller 101, a transfer controller 102, a cache memory 103, a write buffer 104, a magnetic disk device 105, and a battery 106, as in the conventional cache device 1 described above with reference to FIG.
A backup control unit 107 is provided, and a non-volatile memory 108 is additionally provided.

The non-volatile memory 108 is composed of a storage device such as an EEPROM capable of rewriting the stored contents.
The flag F and the data parameter DP are set. The flag F indicates whether or not there is data stored in the write buffer 104, that is, data that can be written in the magnetic disk device 105. The data parameter DP indicates the amount of data stored in the write buffer 104, that is, the amount of data that can be written to the magnetic disk device 105.

The main control unit 101 includes initialization control means 101a,
Response control means 101b and comparison means 101c are provided. The initialization control means 101a outputs the comparison result output by the backup control unit 107 when the setting control of the flag F and the data parameter DP and the startup processing of the cache device 11 are performed.
When 209 is set to valid, the content of flag F is valid,
Alternatively, the initialization control of the write buffer 104 is performed when the comparison means 101c described later is activated.

The write buffer 10 controls the setting of the flag F.
The contents are set valid each time data is written to 4. Also, the contents are invalid only when it is confirmed that the data that can be written to the magnetic disk device 105 is not stored in the write buffer 104 as a result of the data read from the write buffer 104 (data writing to the magnetic disk device 105). Is set to.

The initialization control means 101a includes a main control unit 101
The storage device such as the upper register is also controlled to store the abnormality occurrence information indicating the occurrence of the backup abnormality. At this time, whether the backup abnormality has occurred while the data is stored in the write buffer 104 or not. , In other words,
Information indicating whether or not the write buffer 104 has been initialized is attached.

The response control means 101b performs control for notifying the host computer 2 of the content of the abnormality occurrence information after the start-up processing is completed. The timing of this notification is for the command first accepted from the host computer 2 after the start-up processing is completed, or for the cache device 11
It is assumed that a command or the like that prompts notification of the operation history (log) is received.

The comparison means 101c controls the calculation of the amount of data stored in the write buffer 104 at the time of start-up processing and comparison with the content of the data parameter DP.
If the comparison result is a mismatch, the initialization control means 101a is activated.

The operation of the cache device 11 having the above configuration will be described with reference to the drawings starting from FIG. Figure 6
3 is a first flowchart according to the present invention. Steps S21 to S26 shown in the figure have the same processing contents as steps S1 to S6 described above with reference to FIG. Therefore, the processing from step S27 will be described here.

In step S27, initialization control means
101a accesses the non-volatile memory 108 and reads the content of the flag F. Then, it is determined whether the content of the flag F is valid or invalid, that is, whether or not a backup abnormality has occurred while data is stored in the write buffer 104 (step S28). As a result of step S28,
If the flag F is invalid, that is, if no data is stored, the initialization control means 101a initializes the write buffer 104 (step S29), and finishes the startup processing.

On the other hand, as a result of the step S28, if the flag F is valid, that is, the data is stored, the initialization control means 101a stores the abnormality occurrence information indicating the backup abnormality of the write buffer 104 in the register on the main control unit 101. (Step S30), and the start-up process ends. When the startup process accompanied with the execution of step S30 is executed,
When the command is first received from the host computer 2 after the start-up process is completed, the main control unit 101 executes the process described above with reference to FIG. 5 and reports a backup abnormality to the host computer 2.

In the above processing, if no data is stored in the write buffer 104 even if a backup error occurs, the cache device 11 independently initializes the write buffer 104, and immediately the cache device 11 is initialized. Establish an environment in which the original operation can be performed.

Next, FIG. 7 is a second flowchart according to the present invention. Steps S31 to S40 shown in the figure are
This is the same processing as steps S21 to S30 described above with reference to FIG. Here, after performing step S39,
The initialization control unit 101a stores in the register of the main control unit 101 that the backup abnormality has occurred in a state where no data is stored in the write buffer 104, and ends the process.

The operation when the cache device 11 receives a command from the host computer 2 after the processing of FIG. 7 is executed will be described with reference to FIG. Figure 8
FIG. 6 is a third flowchart according to the present invention. Steps S51 to S55 shown in the figure are the same processes as steps S11 to S15 described above with reference to FIG. Here, description will be given after the execution of step S55. The report in step S53 is made by the response control means 101b.
It is implemented under the control of.

In step S55, the host computer 2
When the command sent by is executed, the initialization control means 101a
Determines whether or not the abnormality occurrence information indicating the backup abnormality (data not stored) is stored in the register of the main control unit 101 (step S56). If the result of determination is that there is memory, the response control means 101b is driven.

Upon receiving the drive, the response control means 101b reports a backup abnormality (no data) to the host computer 2 (step S57), and erases the abnormality occurrence information stored in the register (step S58). , The process ends. If the result of step S56 is that there is no memory, the process is immediately terminated.

In the above processing, the write buffer 10
There is no problem with the data on the magnetic disk device 105, because the host computer 2 is notified of the occurrence of a backup error by dividing the case where no data is stored in 4 and the case where data is stored. It is possible to cause the host computer 2 to recognize a situation in which an abnormality has occurred in the battery 106.

Next, a modified example of the processing described in FIG. 8 will be described with reference to FIG. In order to realize the processing described in FIG. 9, the cache device 11
However, the response control means is provided with a function of storing operation history, for example, information (log) capable of analyzing past operation of the cache device 11 such as access time and access content, in response to a log request from the host computer 2. 101b shall report the log. At the time of this report, the abnormality occurrence information on the main control unit 101 is recognized, and the abnormality occurrence information is reported together with the log report.

FIG. 9 is a fourth flowchart according to the present invention. When the main control unit 101 receives a command requesting a log from the host computer 2, the main control unit 101 activates the response control unit 101b. The response control means 101b, for example, reads the log stored in the magnetic disk device 105 and reports it to the host computer 2 (step S61). Then, it is determined whether or not the abnormality occurrence information is stored in the register of the main control unit 101 (step S62). If it is stored as a result of step S62, the host computer 2 is notified that a backup abnormality that does not affect the data of the magnetic disk device 105 has occurred (step S63), and the abnormality occurrence information is erased. (Step S64).

In the case of the above processing, since the occurrence of a backup abnormality that does not affect the data of the magnetic disk device 105 is notified only when the host computer 2 wants to recognize the state of the cache device 11, it has been described above with reference to FIG. The frequency of notification can be reduced and communication between the host computer 2 and the cache device 11 can be reduced as compared with the case where the backup abnormality is reported when the first command is received after the startup processing. ..

Next, a modified example of the process described above with reference to FIG. 6 will be described with reference to FIG. FIG. 10 is a fifth flowchart according to the present invention. When realizing the processing of FIG. 10, the initialization control means 101a uses the data parameter DP instead of the flag F. That is, the write buffer
When writing data to the 104, the contents of the data parameter DP are increased (added) according to the amount of data to be written, and when the data is read from the write buffer 104 and written to the magnetic disk device 105, the amount of data to be read is set. At the same time, the content of the data parameter DP is decreased (subtracted).

Therefore, the data parameter DP always indicates the data amount of the data stored in the write buffer 104, and when the content of the data parameter DP is zero, the write buffer 104 is written in the magnetic disk device 105. This indicates a state in which the data to be inserted is not stored.

The processing of steps S71 to S74 in FIG. 10 is the same as the processing of steps S21 to S24 shown in FIG. Here, the process after performing step S74 (branch of step S72) will be described. When it is determined in step S74 that the data is normal, the comparison means 101c is activated, and the amount of data is calculated based on the content (data) stored in the write buffer 104 (step S74).
75). When the calculation is completed, the comparing means 101c recognizes the content of the data parameter DP, determines whether or not the result matches the calculated result, and notifies the initialization control means 101a of the determination result (step S76). When the initialization control unit 101a receives the determination result of the coincidence, it determines that the backup is normal (step S77) and ends the process. In addition,
In step S76, if the content of the data parameter DP is zero, the determination result of coincidence is unconditionally notified.

If a mismatch is determined in step S76 (reference voltage Va or less in step S72, an error is determined in step S74), the initialization control means 101a determines a backup abnormality. (Step S78), the data parameter D
The contents of P are recognized (step S79), and it is determined whether the contents are zero, that is, whether the write buffer 104 has data that can be written in the magnetic disk device 105 (step S80).

When it is determined in step S80 that there is no data, the initialization control means 101a initializes the write buffer 104 (step S81) and ends the process. If the result of step S80 indicates that there is data, the initialization control means 101a stores the abnormality occurrence information indicating the backup abnormality in the register of the main control unit 101 (step S82), and ends the processing. ..

In the case of the above processing, the data parameter D is written according to the writing and reading of data in the write buffer 104.
Since it suffices to increase / decrease P, the write buffer 10 is used to determine whether to set the flag F to be valid or invalid.
Since it is not necessary to analyze whether or not data is stored in 4, it is possible to realize simplification of processing. In addition,
The processing described above with reference to FIGS. 7 to 9 can also be realized when the processing described with reference to FIG. 10 is applied.

The present invention is not limited to the above embodiments. In the embodiment, the non-volatile memory 108 for setting the flag F and the data parameter DP is provided independently, but
For example, when an area for setting the flag F and the data parameter DP can be secured on the magnetic disk device 105, the magnetic disk device 105 can be used as a non-volatile memory for setting the flag F and the data parameter DP. is there. Further, in the embodiment, the magnetic disk device 105 has been described as an example of the storage medium to be cached. However, for example, high speed data writing including a mechanical operation in the access time of a rewritable optical disk device or the like is performed. The present invention can be applied to any device as long as it is difficult to realize the (reading) process.

[0051]

As described above, according to the cache device of the present invention, the write buffer is initialized immediately for a backup abnormality that occurs when no data is stored in the write buffer, and the original operation of the cache device is performed. In order to set the cache device to a state in which the cache device is enabled, the cache device can be swiftly executed without performing the procedure of performing the original operation of the cache device after performing an analysis of whether or not a backup abnormality has occurred in the state where data is not stored in the write buffer The operation of can be resumed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a cache device of the present invention.

FIG. 2 is a conceptual diagram of a conventional cache device.

FIG. 3 is a circuit diagram of a backup control unit.

FIG. 4 is a first flowchart of a conventional startup process.

FIG. 5 is a second flowchart of a conventional startup process.

FIG. 6 is a first flowchart according to the present invention.

FIG. 7 is a second flowchart according to the present invention.

FIG. 8 is a third flowchart according to the present invention.

FIG. 9 is a fourth flowchart according to the present invention.

FIG. 10 is a fifth flowchart according to the present invention.

[Explanation of symbols]

 11 cache device 101 main controller 101a initialization controller 101b response controller 101c comparing device 104 write buffer 105 magnetic disk device 106 battery 107 backup controller

Claims (3)

[Claims] 1. A write buffer that temporarily stores data to be written to a storage device, a battery that backs up the write buffer, a backup control unit that detects an abnormality in the backup, and the data is stored in the write buffer. A non-volatile memory that stores a flag indicating that the data has been stored, and when the abnormality is detected, the flag is referred to. If the flag indicates that the data has not been stored, the write buffer is initialized. A cache device comprising initialization control means for performing. 2. When the access from the host device is accepted after initialization, the backup abnormality is detected,
2. The cache device according to claim 1, further comprising a response control unit that reports to the host device that the initialization has been performed. 3. A write buffer for temporarily storing data to be written to a storage device, a battery for backing up the write buffer, and a data parameter indicating a data amount of the data stored in the write buffer. A non-volatile memory, a backup control unit that detects an abnormality of the backup, and when the abnormality is detected, calculates the data parameter based on the data stored in the write buffer, and stores the data in the non-volatile memory. When the comparison means for comparing with the stored data parameter and the comparison result do not match and the data parameter stored in the non-volatile memory indicates that no data is stored, the initialization of the write buffer is performed. 2. The cache device according to claim 1, further comprising: .