JPH05204552A - Data write system - Google Patents

Abstract

PURPOSE:To prevent the down of the whole of the auxiliary storage device side even at the time of the occurrence of a failure in a data compressing circuit. CONSTITUTION:When compression is indicated from a higher-order device 20, a transfer control circuit 11b of a magnetic tape controller 10 inputs data inputted from the higher-order device to a data compressing and restoring circuit 11d, and this circuit 11d subjects input data to compression processing and outputs this data to a magnetic tape device 30 through a transfer control circuit to write it on a magnetic tape. An error detection part lid-4 monitors the occurrence of error at the time of data compression; and if data compression error is detected, the transfer control circuit 11b outputs retransmitted data to the magnetic tape device 30 without compressing to write it on the magnetic tape. Thus, data is written on the magnetic tape without being compressed even when correct data compression is impossible because of a failure, and the down of the whole of the controller is prevented to continue the processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data writing method, and more particularly to a data writing method for compressing input data according to an instruction from a host or writing it in a storage device without compression.

[0002]

2. Description of the Related Art When data is written to a magnetic tape device, which is an auxiliary storage device in a computer system,
Compress data according to a predetermined algorithm and write it,
When reading, the original data is restored from the compressed data. By such compression / decompression, a large amount of data can be recorded, which is particularly effective for a cartridge type small tape.

In 1989, ANSI (American Nationa
l Standard Institution) proposes a control method of a technique for increasing the recording amount per cartridge tape. In this control technology, first, Binary Arithmetic Codin
The logical data sent from the host is compressed by the data compression theory called g: BAC). Then,
I existing between a block and a block (logical data) of a tape written by a conventional magnetic tape device
BG (Internal Block Gap) is omitted and a plurality of data blocks are written on the tape as one data block. Each logical data is compressed, and information necessary for control (packet header, packet trailer) is added to each packet to form a packet. At the end of one or more packets, control information called a count field Is added. And this format (Extend M
It is defined so that compressed data and uncompressed raw data packets can be mixed and controlled.

FIG. 5 and FIG. 6 show Ex proposed by ANSI.
It is explanatory drawing of tend Magnetic Tape Format. It is composed of an N-byte data block 1, a 4-byte data block identifier 2, and a PAD 3 of 0 to 13 bytes.
In the magnetic tape, 14 bytes are written in the width direction and continuously written in the longitudinal direction. Therefore, the magnetic tape may be less than 14 bytes at the end of the data block. The PAD 3 is written in the empty area to eliminate the empty area.

The data block 1 is composed of one or a plurality of packets 1a, 1b, ... 1m and a count field 1n of 6 bytes, and each packet is composed of a packet header PH, data DT and a packet trailer PT, and a count field 1n. The number of packets forming the data block 1 and the total number of bytes are written in.

The data block identifier 2 is a 1-byte sector number SN, a 2-bit ("10") fixed pattern indicating the Extend Magnetic Tape Format, and a physical block identifier PBI (3 bytes are formed by the fixed pattern). It consists of and. The packet header PH includes a 6-byte block identifier 4a and a packet offset 4b.
A 1-byte packet trailer length 4c indicating the length of the packet trailer, a 1-byte flag 4d indicating whether the data DT is compressed data or uncompressed data, and 1
It is composed of an unused portion (reserve) 4e of 8 bytes and a cyclic redundancy code CRC 4f of 2 bytes.

The packet trailer PT has two formats depending on whether the data DT is uncompressed data or uncompressed data. In the case of uncompressed data, a trailer PAD5a of 0 to 31 bytes and a packet CRC5b are provided. Composed of. In the case of compressed data, (1) a logical block length 6a, which is the number of bytes of the logical data (raw data) before compression, and (2) a logical block CRC 6b from the compressed data DT to the logical block length 6a. , (3) Compressed block CR
C6c and (4) 0-31 byte trailer PAD6d
And (5) packet CRC6e.

[0008]

According to the control technique proposed in this way, it is possible to control even if packets of compressed data and uncompressed raw data are mixed.
However, in the conventional magnetic tape control device to which such a control technique is applied, there is a problem that if the BAC circuit that performs data compression fails, the entire magnetic tape control device goes down. In view of the above, an object of the present invention is to provide a data writing method in which the auxiliary storage control device, for example, the entire magnetic tape control device, does not go down even if a failure occurs in the data compression circuit.

[0009]

FIG. 1 illustrates the principle of the present invention. 10 is a magnetic tape controller, 20 is a host,
A host device such as a channel, and 30 are magnetic tape devices.
In the magnetic tape control device, 11b is a transfer control circuit that controls data transfer, and 11d is a data compression / decompression circuit that compresses data from a host device and restores the compressed data read from the magnetic tape. An error detection unit 11d-4 that detects an error is provided.

[0010]

When the compression instruction is given from the host device 20, the transfer control circuit 11b of the magnetic tape controller 10 inputs the data input from the host device to the data compression / decompression circuit 11d, and the data compression / decompression circuit 11d inputs it. The data is compressed and output to the magnetic tape device 30 via the transfer control circuit to be written on the magnetic tape. The error detection unit 11d-4 monitors whether an error has occurred during data compression. If a data compression error is detected, the transfer control circuit 11b outputs the input data to the magnetic tape device 30 without compressing it. , Retry writing to the magnetic tape. By doing so, even if the data cannot be compressed correctly due to a failure, the data can be written to the magnetic tape without compression, and the processing can be continued without the entire magnetic tape controller going down. it can.

Further, the number of times data is written to the magnetic tape without compression due to the occurrence of a compression error is monitored, and when the number of times reaches a prescribed number in the same job, the upper device is notified of system performance deterioration. If you do, maintenance of the device appropriately,
It can be repaired, and it can be prevented from operating in a state of degraded performance.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is an overall configuration diagram of a magnetic tape control apparatus according to the present invention. 11 is a host interface control section, 12 is a buffer for storing data and control information, and 13 is a formatter section. Host interface control unit In the host interface control unit 11, 11a is a channel interface circuit, 11b is a transfer control circuit that controls data transfer, 11c is an internal bus adapter,
Reference numeral 1d is a data compression / decompression circuit that compresses data from the host device and restores the compressed data read from the magnetic tape, and 11e is a host interface control processor that controls the entire host interface control unit.

(A) Channel Interface Circuit The channel interface circuit 11a administers an interface with a channel which is a host device. When writing data, control information (including a compression instruction) and logical data are sequentially sent from the host device, so the transfer control circuit 11b takes in the logical data via the channel interface circuit 11a. In addition, the host interface control processor 11e takes in control information via the channel interface circuit 11a and performs predetermined control, and at the same time, receives status information indicating a write result every time logical data is received to the host device via the channel interface circuit 11a. Notice.

(B) Transfer Control Circuit The transfer control circuit 11b selects a transfer sequence control circuit 11b-1 for controlling the transfer sequence of data and one of compressed data and non-compressed data when writing the data to the magnetic tape. A switching circuit 11b-2 for outputting, a switching circuit 11b-3 for selecting and outputting one of the unrestored data and the one restored by the restoration circuit when transferring the data from the magnetic tape to the host device, and the internal circuit Internal bus adapter control circuit for controlling data transmission / reception to / from the bus adapter 11c
(IBA control circuit) 11b-4. The transfer sequence control circuit 11b-1 has an error detecting function, and when an error is detected, it is notified to the host interface control processor 11e.

(C) Compressing / decompressing circuit The compressing / decompressing circuit 11d receives a command from the host interface / control processor 11e to compress input data, and a compressing circuit 11d-1 from the host interface / control processor 11e. Decompression circuit 11 that decompresses compressed data to original data according to an instruction
d-2 and a switching circuit that selects / outputs the compressed data output from the compression circuit 11d-1 during compression and selects / outputs the data when transferring the data from the magnetic tape to the host device.
The decompression circuit 11d-2 includes an error detection unit 11d-4 that detects whether the compression process is normal or abnormal.

The compression circuit 11d-1 compresses the input logical data according to a predetermined algorithm, and at the same time, the logical block length 6a in the packet trailer PT (see FIG. 6).
And a logical block CRC6b are created, these are added to the compressed data and output. The error detection unit 11d-4 checks whether the restored logical block length (byte number) matches the logical block length before compression (byte number), and also performs a CRC check by the logical block CRC. Alternatively, if a CRC check error is detected, it is determined that an error has occurred in the data compression processing by the compression circuit 11d, and the host interface / control processor 11e is notified of the error occurrence.

(D) Host interface control processor 11 Host interface control processor 11
e is for controlling the entire host interface control unit, and when the control information such as whether or not to compress the data from the host device is taken in via the channel interface circuit 11a and the data is compressed, it is stored in the compression circuit 11d-1. The compression circuit is instructed to be executed, and the switching circuit 11b-2 and the switching circuit 11d-3 are instructed to select the compression circuit output. When the data is not compressed, the switching circuit 11b-2 is instructed to select the uncompressed data output from the transfer sequence control circuit 11b-1. Also, the host interface control processor 11e receives a normal end, an error end, and
The higher-level device is notified of status information including data instructing retransmission request, performance degradation, and the like.

Furthermore, the host interface control processor 11e exchanges control data with the processor of the formatter unit 12 via the control information table 12a of the buffer 12. For example, the control information indicating whether the data written in the buffer 12 from the host device is compressed or not is written in the table 12a. In addition, the formatter unit 13 reads the control information written in the control information table 12a (control information indicating whether the data input from the magnetic tape side is compressed data or non-compressed data). When the data from the magnetic tape device is compressed data, the switching circuit 11d-3 is instructed to select the data from the IBA control circuit 11b-4 and the decompression circuit 11d-2 is decompressed. The execution of the process is instructed, and the switching circuit 11b-3 is instructed to select the restoration circuit output. In the case of uncompressed data, the switching circuit 11b-3 is connected to the IB
Instruct to select the data from the A control circuit 11b-4.

Formatter section The formatter section 13 comprises an internal bus adapter 13a, a formatter section 13b for performing format conversion, and a format control processor 13c for controlling the entire formatter section. The formatter 13b adds a packet header, a packet trailer, etc. to the packet sent from the transfer control circuit 11b at the time of writing data, and converts the packet into the format shown in FIGS.
These are removed from the data input from the magnetic tape device side. Further, the formatter 13b rearranges the data input in byte units at the time of writing and outputs it in parallel to the magnetic tape device side in units of 14 bits, and rearranges the data input in the unit of 14 bits at the time of reading. Output 1 byte at a time. 3A and 3B are explanatory diagrams of data rearrangement of the formatter 13b, FIG. 3A is an explanatory diagram of data writing state on the magnetic tape, and FIG. 3B is an explanatory diagram of data rearrangement operation in the formatter 13b.

As shown in FIG. 3 (a), there are 18 tracks (4 tracks ECCT on both sides) on the magnetic tape MT.
_{1 to} ECCT ₂ are provided with ECC check character tracks), and data is continuously recorded in the longitudinal direction.
That is, the magnetic head moves 18 in the width direction of the magnetic tape.
Data is written simultaneously bit by bit, and 18 bytes are recorded by eight write operations. Therefore, the formatter unit 13b uses the internal bus adapter 13 when writing data.
Format conversion is performed on the data retrieved from the buffer 12 via a, and 14 bytes are arranged as shown in FIG. 3 (b) and an ECC check character is added.
18 bits are output in parallel to the magnetic tape device side. When reading the data, the ECC check character is deleted from the data input in 18-bit units from the magnetic tape unit, 14 bytes are arranged as shown in Fig. 3 (b), and then 1 byte is read, and the original data is read. Writing to the buffer 12 via the internal bus adapter 13a while returning to the format.

[0021] Buffer buffer 12 at the time of data writing to the magnetic tape, the data stored temporarily via the internal bus adapter 11c of the host interface control unit 11, sequentially through the internal bus adapter 13a of the formatter unit 13 Read. Further, the data from the magnetic tape device side is temporarily stored via the internal bus adapter 13a of the formatter unit and sequentially read via the internal bus adapter 11c of the host interface control unit.

The buffer 12 has a control information table 12a.
Are provided, and the host interface control processor 11e and the format control processor 13c mutually exchange control information via the control information table 12a. For example, the format control processor 11e refers to the flag 4d (FIG. 6) included in the data input from the magnetic tape device side to determine whether the data is compressed or uncompressed, and outputs the determination result internally. The data is written in the control information table 12a via the bus adapter 13a, and the host interface control processor 11e reads the determination result via the internal bus adapter 11c to determine whether the data is compressed or uncompressed.

Overall operation (a) When writing without compression Host interface control processor 11
When there is an instruction of non-compression by the control information from the host device, e transfers the logical data sent from the host device to the transfer sequence control circuit 11b-1 → the switching circuit 11b-2 → the IBA control circuit 11b-4 → Buffer 1 via internal bus adapter 11c
2, the formatter unit 13 controls the format conversion and rearrangement, and outputs the data to the magnetic tape device to write it on the magnetic tape.

(B) When compressing and writing When a compression instruction is given by the control information from the host device, the host interface control processor 11e
Instructs the compression circuit 11d-1 to execute compression processing, and instructs the switching circuit 11b-2 and the switching circuit 11d-3 to select the compression circuit output. This allows the compression circuit
11d-1 compresses the logical data input from the host device via the channel interface circuit 11a and the transfer control circuit 11b, and at the same time the logical block length 6a
(FIG. 6) and the logical block CRC6b are generated and added to the compressed data, and the switching circuit 11b-2 → the IBA control circuit 11b-4 →
Write to the buffer 12 via the internal bus adapter 11c (step 101).

In parallel with this, the decompression circuit 11d-2 decompresses the compressed data input from the switching circuit 11d-3 to decompress it. Further, the error detection unit 11d-4 performs a CRC check based on the logical block CRC added to the compressed data, and similarly, the number of bytes indicated by the logical block length 6a added to the compressed data and the restored logic. Check if the number of bytes in the block matches (Step 1
02). If there is no CRC check error and the number of bytes matches, it is judged that the data compression has been completed normally, and the host interface control processor
The normal end of compression is notified to the host device and the formatter unit 13 via 11e. The formatter unit 13 performs format conversion and rearrangement in response to the normal end notification, outputs it to the magnetic tape device side, and writes it on the magnetic tape. After that, the host interface control processor 11e
Repeats the processing from step 101 onward for the next logical data.

However, in step 102, the CRC
If there is a check error or if the number of bytes does not match, it is determined that an error has occurred in the data compression processing by the compression circuit 11d, and the error occurrence is notified to the host interface control processor 11e. The host interface control processor 11e notifies the formatter unit 13 of the data compression failure, requests the upper device to retransmit the logical data according to the status information, and performs the compression circuit 11d-1 to perform the data compression process on the retransmitted logical data. Is retried (step 103). Then, it is judged whether or not the retry of the data compression is normally performed (step 104), and if the retry is normally completed, thereafter, the step 101 is performed on the next logical data.
The subsequent processing is repeated.

However, if an error occurs due to the retry of data compression, it is checked whether the specified number of times of retry (for example, 2 times) has been performed (step 105), and if the specified number of times of retry has not been performed, step 103 is performed. Return to and repeat the retry. If an error occurs even after retrying the specified number of times, it is judged that the compression circuit 11d-1 has a failure, and a request to retransmit the logical data to the host device is made, and the compression circuit is skipped. Then, the retransmitted data is written (without data compression) (step 106).

It is monitored whether or not an error has occurred during the process of writing the retransmitted data (step 107). If the error is normal, the retry count for performance degradation (which is 0 at the start of the job) is incremented by 1 (step 10).
8). A job is a job from the time the power is supplied to the magnetic tape control unit to the time the power is cut off. When the power is supplied, the number of retries for performance degradation is initially set to zero. Next, the number of times the performance degradation is retried is the specified number of times (for example, 1
28) is checked (step 109), and if the specified number of times has not been reached, the processing from step 101 onward is repeated for the next logical data.

However, in step 109, if the number of times of retry of performance degradation has reached the specified number of times, the performance information is notified to the host by the status information (step 11).
0). This completes the writing of the logical data, but waits for an instruction from the host as to whether to continue the job thereafter, that is, whether to continue writing the data to the magnetic tape controller or interrupt it (step 11).
1). Incidentally, the host reports the performance degradation to instruct the maintenance and repair of the device as appropriate to prevent the operation from continuing with the performance degradation.

On the other hand, in step 107, if an error occurs during the retry without data compression, it is checked whether or not the retry has been executed a specified number of times (eg, 3 times) (step 112). The retries after 106 are repeated, and if the specified number of times is reached, an error is reported to the host (step 113) and the processing ends in error.

(C) Data reading When data is read from the magnetic tape and transferred to the host, the data input from the magnetic tape device side is rearranged and format-converted by the formatter unit 13 and stored in the buffer 12. In parallel with this, the format control processor 13c makes a judgment for each packet whether it is compressed data or non-compressed data, writes the judgment result in the control information table 12a, and the host interface control processor 11e reads the judgment result.

When the data sent from the magnetic tape unit is uncompressed data, the host interface control processor 11e operates the switching circuit 11b-3 to make the buffer 12 → the internal bus adapter 11c → the IBA control circuit 11b. The data input via -4 is selected and thereafter transferred to the host via the transfer sequence control circuit 11b-1 and the channel interface circuit 11a.

On the other hand, in the case of compressed data, the switching circuit 11
The d-3 is instructed to select the data from the IBA control circuit 11b-4, the restoration circuit 11d-2 is instructed to execute the restoration process, and the switching circuit 11b-3 is selected to output the restoration circuit. Instruct them to do so. As a result, the decompression circuit 11d-2 decompresses the compressed data and transfers it to the host via the switching circuit 11b-3 → transfer sequence control circuit 11b-1 → channel interface circuit 11a.

Although the case where the present invention is applied to the magnetic tape control device has been described above, the present invention is not limited to this and can be applied to a disk control device, a semiconductor control device and the like. Although the present invention has been described above with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these.

[0035]

As described above, according to the present invention, in the data writing method of compressing the input data according to the instruction from the host device or writing the data to the storage device without compressing the data, a compression error occurs when the data is compressed and written by the compression instruction. It is configured to write the input data to the storage device without compression when a compression error occurs, so even if the data compression cannot be performed correctly due to a failure,
Data can be written to the storage device without compression, and the entire auxiliary storage control device side does not go down, and the processing can be continued.

Further, since the number of times of non-compressed data writing to the storage device due to the occurrence of a compression error is monitored and the number of times reaches the specified number, the upper device is notified of system performance deterioration. It is possible to appropriately maintain and repair the device, and prevent the device from being operated in a performance-reduced state.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of data rearrangement of a formatter unit.

FIG. 4 is a flowchart of a data writing process during compression.

FIG. 5 is a first explanatory diagram of an ANSI tape format.

FIG. 6 is a second explanatory diagram of an ANSI tape format.

[Explanation of symbols]

 10 ... Magnetic tape control device 11b ... Transfer control circuit 11d ... Data compression / decompression circuit 11d-4 ... Error detection unit 20 ... Host device 30 ... Magnetic tape device

Claims (2)

[Claims] 1. A data writing method of compressing input data according to an instruction from a higher-level device or writing the data to a storage device without compression, and monitoring a data compression error at the time of data compression writing by a compression instruction, and generating a data compression error. When writing, the data writing method is characterized by writing the input data to the storage device without compressing it. 2. The number of times input data is written without being compressed due to a data compression error occurring, and when the number of times reaches a prescribed number, a higher-level device is notified of system performance deterioration. 1. The data writing method described in 1.