JP2835844B2 - Magnetic tape unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic tape device with a buffer of an industry standard interface in which data transfer is performed with a higher model, for example, a host computer. The present invention relates to a magnetic tape device that processes a write data block (hereinafter, referred to as a write pending block) that exists in a buffer of the magnetic tape device and has not been written on the magnetic tape in operation.

[Conventional technology]

In the magnetic tape device used as an external storage device of a computer, the use of a magnetic disk or the like for backup is increasing, the price is low, and the tape running is controlled directly by a reel motor due to a demand for high speed tape running. 2. Description of the Related Art A method of continuously running a tape without stopping running in a blank portion (IBG) between a data block and an adjacent data block for each data block, that is, a streaming method has been widely used.

A streaming magnetic tape device with a buffer has a data buffer in the magnetic tape device so that data transfer with the host device and data processing on the magnetic tape can be performed asynchronously. Instructions can be issued without being aware, and conversely, a magnetic tape device can operate continuously without waiting for an instruction from the host device, so the operating efficiency of the streaming mode is improved, and the overall processing efficiency is improved. An improvement is obtained.

As an interface of the magnetic tape device, there is an industry standard interface generally used from the start / stop magnetic tape device era to the present. In recent years, it is a general-purpose interface
Although the number of magnetic tape devices of SCSI (Small Computer System Interface) tends to increase, there is also a great demand for an industry standard interface that can use a conventional host adapter and driver software.

Generally, when an unrecoverable error occurs due to a medium error during a write operation to a tape, the host device closes the volume and transfers data that could not be written on the tape to another tape. Write recovery work is required.

If the error occurs during the write operation of the buffered magnetic tape device, the writing from the data buffer to the tape stops, so the data transfer from the host device is not stored in the data buffer of the magnetic tape device. Has been completed normally, and there is a write data block that has not yet been actually written on the tape, that is, a write bending block.

In an industry standard interface buffered magnetic tape unit, if an unrecoverable error such as described above occurs in the presence of this write pending block, the host device will look farther ahead on the interface. Since normal data transfer has been completed up to the write data block, it cannot be determined which write data block has actually been written on the tape.

As a method of allowing the host device to know the write error occurrence position on the tape to some extent, for example, as a command of the interface, a magnetic tape device which can use an instruction to write all the write pending blocks onto the tape, or A magnetic tape device having a function of writing all write pending blocks onto a tape when a write file mark instruction is executed has been used.

As a conventional recovery operation, there has been adopted a method of exchanging a tape and restarting the volume processing from the beginning, and a method of reading a tape in which an error has occurred from the beginning and checking the state of a block before processing.

[Problems to be solved by the invention]

In the case of a magnetic tape device using a method capable of knowing the write error occurrence position in a conventional host device example,
In a certain number of block units, the write data on the tape
The block can be managed by the host device, but in order to effectively use the above functions, all or a certain amount of the transferred data must be left in the data buffer of the host device. However, there is a disadvantage that an extra buffer amount is required on the host device side in order not to reduce the processing speed in the host device. In order to reduce this extra buffer amount and to know the write error occurrence position on the tape more accurately, the above-mentioned function may be frequently used.
This leads to a reduction in the overall processing speed and reduces the advantage of using a magnetic tape device with a buffer.

Further, the magnetic tape device with buffer of the industry standard interface using the conventional recovery work method has the following disadvantages. In other words, the host device has to prepare data of the same volume again, and it takes a long time to process the data, so that the load on the host device is increased.

An object of the present invention is to solve the above-described drawbacks, and efficiently transfers data as a buffered magnetic tape device during normal operation, and when an irrecoverable write error occurs during tape write operation,
The status information including the number of write pending blocks remaining in the buffer of the magnetic tape device is sent to the host device, and the data of the write pending block remaining in the buffer is transferred to the host device. Accordingly, it is possible to provide an industry standard interface compliant buffered magnetic tape device which can perform recovery work without preparing the data of the volume again on the host device side or having an extra buffer. The purpose is.

[Means for solving the problem]

In order to achieve the above object, the magnetic tape device of the present invention has an industry standard interface,
In a magnetic tape device having a buffer memory, at least a predetermined first code other than a standard command code of an industry standard interface is used.
Command decoding means for interpreting the first and second command codes and outputting first and second control signals corresponding thereto, and when receiving a first control signal from the command decoding means, Status creation means for outputting a status including block information in the buffer memory in a data format; and when receiving a first control signal from the command decoding means,
Outputs information of a write data block existing in the memory and not yet written on the tape to the status creating means, and from the command decoding means,
When receiving the second control signal, the buffer memory is controlled so as to sequentially output the data of the write data block existing in the buffer memory and not yet written on the tape to the host interface side. Light pending block management means;
When a data block exists in the buffer memory, the data of the write data block read from the buffer memory is written on the tape in block units, and the data of the write data block is written on the tape. A magnetic tape drive that generates a write error signal when writing to the
Data transmission means for outputting an error signal, the output of the status creation means and the output of the write pending block management means to a read data line of a host interface.

Then, the status creating means includes a buffer
Status data may be created in a free area of the memory.

(Operation)

When the data of the block transferred from the host device to the buffer cannot be written on the tape by the buffered magnetic tape device and an unrecoverable error occurs, the occurrence of a write error is notified to the host device. The host device sends the first and second commands to the magnetic tape device, requests status information in the buffer, and requests data transfer of a write pending block in the buffer. The magnetic tape device sequentially transfers the data of the write pending block in the buffer left unwritten on the tape in response to a request from the host device. Therefore, of the write data blocks sent to the magnetic tape device side, data equal to or less than the write data blocks left unwritten on the tape are transferred to the buffer on the host device side.

An embodiment of the present invention will be described below with reference to the drawings.

〔Example〕

FIG. 1 is a block diagram of an embodiment of a magnetic tape device according to the present invention, FIG. 2 is a flowchart of an embodiment showing the operation of FIG. 1, and FIGS. 3 (I) to (IV) are pointers of a buffer memory. FIG.

In FIG. 1, 1 is a command decoding unit, 2 is a data transmission unit, 3 is a buffer control unit, 4 is a status creation unit, 5 is a write pending block management unit, 6 is a buffer memory, and 7 is a magnetic tape.・ It is a drive unit.

The command decoding means 1 interprets predetermined first and second command codes in addition to industry standard interface standard command codes sent from a host device (not shown). From the first command code, the state of the inside of the magnetic tape device, particularly from the first control signal for transmitting the block information in the buffer memory 6 to the host device, and from the second command code The data of a block which has not been written on the tape of the magnetic tape device yet exists in the buffer memory 6, i.e., the write pending data.
A second control signal for transferring the data of the block to the host device is generated.

The data transmission means 2 is a buffer control means 3 described below.
This is a circuit unit for transferring the block information in the buffer memory 6 created by the status creating unit 4 and the data of the write pending block remaining in the buffer memory 6 to the host device in response to an instruction from the host.

The buffer control means 3 includes a status creation means 4 and a write / ending block management means 5 which will be described below. The data and buffer memory created by the buffer control means 3 in response to an input control signal. The data stored in the buffer memory 6 is sent to the data transmitting means 2 and the memory management of the buffer memory 6 is performed.

When receiving the first control signal from the command decoding means 1, the status creation means 4 includes the block information such as the state of the write pending blocks in the buffer memory 6 and the number of remaining blocks. The status is created in a data format, and is transmitted to a host device (not shown) by the data transmission means 2.

The write pending block management unit 5 transfers the information of the write data block stored in the buffer memory 6 to the status creation unit 4 when the first control signal arrives, and also executes the second control Each time a signal arrives, a write pending
Control for transferring the data of the block to the data transmitting means 2 is performed.

The buffer memory 6 stores each data of the write data block sent from the host device in block units, and reads out the data in block units. The data of the write data block read in units of this block is written on the tape. The data in the block unit written on the tape is updated with the data of the write data block which is sequentially transferred and erased, so that a write error occurs and the data can be written on the tape. When the data is exhausted, the prefetched block unit data remains in the buffer memory 6.

The magnetic tape drive unit 7 sequentially writes each data of the write data block read from the buffer memory 6 on the tape for each unit block.

Next, the flowchart of FIG. 2 and the buffer buffer of FIG.
The operation of FIG. 1 will be described with reference to an explanatory diagram of a memory pointer.

The magnetic tape drive unit 7 sequentially writes the data in block units read from the buffer memory 6 on the tape. Assuming that the write data blocks # 1 to # 10 are transferred from the host device and stored in the buffer memory 6 as shown in FIG. 3 (I), for example, The host head pointer HH indicating whether data has been sent to the magnetic tape unit up to the block is #
10 blocks to the right. When the data in blocks read from the buffer memory 6 is written on the tape of the magnetic tape drive unit 7, the tape head pointer TH indicating the corresponding position of the tape head of the magnetic tape drive unit 7 moves to the right. Move one block at a time.

When a write data block to be written exists in the buffer memory 6 (step 1), the magnetic tape device, that is, the magnetic tape drive unit 7, stores the data of the block read from the buffer memory 6 on the tape. Writing is performed sequentially in block units (step 2). When the # 4 write data block cannot be normally written on the tape for some reason, the magnetic tape drive unit 7 returns the tape head by the # 4 write data block, and then returns to the tape. Is written. In this write operation again, the # 4 write data
When the data of the block cannot be normally written on the tape (step 3), as shown in FIG. 3 (II), the tape head pointer TH is set for the # 4 write data block, that is, # 3. It returns to the right end of the write data block, and notifies the host device of the occurrence of a write error (step 4). # In the rewriting
When the data of the four write data blocks can be normally written on the tape (step 3), the write processing of the # 5 write data block and the subsequent ones is continued (steps 1 and 2).

When receiving a write error from the magnetic tape device, the host device transmits a first command code to the magnetic tape device in order to know the state of the magnetic tape device. The first command code is received by the command decoding means 1, interpreted, and
Is transmitted to the buffer control means 3 (step 5). Status creation means 4 of the buffer control means 3
Is sent to the write pending block management means 5 which manages the buffer memory 6.
The number of write pending blocks or the position of an error block in which a write error has occurred, that is, the position of the tape head pointer TH and the position of the host head pointer HH are queried. From these information, a status indicating the status of the magnetic tape device including the number of write pending blocks in the buffer memory 6 in the current status is created in a data format (step 6), and the host device is transmitted via the data transmission means 2 to the host device. Immediately transmit to the side (step 7). As another method of transmitting the status, a free area of the buffer memory 6, for example, in the example shown in FIG. 3, a block area below the # 11 write data block indicated by the host head pointer HH is free. Since it is an area, information data indicating the status of the magnetic tape device in the data format created by the status creating means 4 is temporarily stored in the empty area, read out at an appropriate timing, and read via the data transmitting means 2. There is a method that is sent to the host device (step 7).

When receiving the status information data including the number of write pending blocks from the magnetic tape device, the host device writes the write pending data to the magnetic tape device.
A second command code representing a data transfer request of a write pending block designating a leading block that is a block, that is, a # 4 write data block, is transmitted. The second command code is received by the command decoding means 1, interpreted, and transmits a second control signal to the buffer control means 3 (step 8). Write pending of the buffer control means 3
The block management means 5 receives the second control signal,
Each data in the head block of the write pending block, that is, each data in the # 4 write data block is read, and the read data in the read # 4 write data block is transferred to the buffer on the host device side via the data transmission means 2. Each data is sequentially transferred (step 9).

The host device counts the number of write pending blocks transferred from the magnetic tape device, and the counted number is the number of write / read blocks at the time of the write error previously transmitted from the magnetic tape device. Until the number of pending blocks matches, the second
Issue the command code This allows the buffer
The data of the write pending blocks # 5 to # 10 stored in the memory 6 are sequentially transferred in block units, and all the data of the write pending blocks stored in the buffer memory 6 are all transferred. The data is transferred to the buffer of the host device (step 10). FIG. 3 (IV) shows this state. Each time the data of the write pending block is transferred from the magnetic tape device to the host device side in block units, the tape head pointer TH becomes 1 Move to the right block by block. When the tape head pointer TH reaches the right end of the # 10 write pending block, the data transfer of the write pending block has been completed.

When the data transfer of the write pending block is completed, the host device executes a close process.

Therefore, by exchanging the tape of the magnetic tape device, the host device can immediately transfer each data of the write binding block returned to the host device, and when the magnetic tape device is changed, Also,
Each data of the write pending block returned to the host device can be immediately transferred in block units.

〔The invention's effect〕

As described above, according to the present invention, the information of the write pending block and its data at the time of the write operation are returned to the host device, so that when an unrecoverable error occurs in the write operation to the tape, This eliminates the need for the host device to prepare the data of the entire volume again, and eliminates the need to provide an extra buffer, thereby enabling the recovery operation to be performed efficiently in a short time. Therefore, it is possible to avoid a reduction in the overall processing speed of the host device.

[Brief description of the drawings]

FIG. 1 shows the configuration of an embodiment of a magnetic tape device according to the present invention,
FIG. 2 is a flow chart of an embodiment showing the operation of FIG. 1, and FIGS. 3 (I) to (IV) are pointer explanatory diagrams of a buffer memory. In the figure, 1 is a command decoding means, 2 is a data transmission means, 3 is a buffer control means, 4 is a status creation means,
5 is a write pending block management means, 6 is a buffer memory, and 7 is a magnetic tape drive.

Claims (2)

(57) [Claims] 1. A magnetic tape device having a buffer memory (6) of an industry standard interface, wherein at least a first command code and a first command code which are predetermined in addition to a standard command code of the industry standard interface. Command decoding means (1) for interpreting a second command code and outputting corresponding first and second control signals, and when receiving a first control signal from the command decoding means Status creation means (4) for outputting a status including block information in the buffer memory in a data format; and presence in the buffer memory when a first control signal is received from the command decoding means. The write data block information that has not yet been written on the tape When the second control signal is received from the command decoding means and output from the command decoding means, the data of the write data block existing in the buffer memory and not yet written on the tape is output. A write pending controller for controlling the buffer memory so as to sequentially output to the host interface side;
When the write data block exists in the buffer memory, the block management means (5) writes the data of the write data block read from the buffer memory on a tape basis in block units, A magnetic tape drive unit that generates a write error signal when the data of the write data block cannot be normally written on the tape (7)
And data transmission means (2) for outputting the write error signal, the output of the status creation means and the output of the write pending block management means to a read data line of a host interface. Characteristic magnetic tape device. 2. The magnetic tape device according to claim 1, wherein said status creating means creates status data in a free area of said buffer memory.