JP2504193B2 - Control device with buffer memory - Google Patents

Description

TECHNICAL FIELD The present invention relates to a control device with a buffer memory, and more particularly to a control device with a buffer memory that has a buffer storage area in its own device and is connected to a plurality of lower devices.

2. Description of the Related Art Conventionally, a control device with a buffer memory of this type can control a plurality of lower-level devices, for example, a recording / reproducing mechanism, and a buffer memory composed of the same number of storage areas or less storage areas (segments). Has an area. In particular,
When the lower device is a streamer type magnetic tape device having no mechanical buffer and poor start / stop characteristics, the following operation is performed in order to reduce the number of start / stop.

First, in accordance with a READ / WRITE command from the host device, a segment of the buffer storage area which is not currently in use is assigned to a recording / reproducing mechanism for READ / WRITE. Next, the READ data sent from the recording / reproducing mechanism or the WRITE data sent from the host device is held in the buffer memory. Finally, the data was transferred to the host device or the recording / reproducing mechanism.

However, in the above-mentioned conventional controller with buffer memory,
If the number of recording / reproducing mechanisms is larger than the number of segments in the buffer storage area, READ from a higher-level device to another recording / reproducing mechanism while all segments are assigned to the recording / reproducing mechanisms respectively. When the / WRITE command is issued, all the segments have already been used for other recording / playback mechanisms, so the command cannot be executed until one of the segments becomes empty.

In such a case, the READ / WRITE instruction is put in a waiting state, and as a result, the instruction response speed deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to read from a higher-level device even in a system in which the number of lower-level devices is larger than the number of segments in the buffer storage area. Another object of the present invention is to provide a control device with a buffer memory that enables control without waiting for a / WRITE command.

Configuration of the Invention A control device with a buffer memory according to the present invention is a control device with a buffer memory connected to N lower devices,
M (2 ≦ M <for performing data exchange with each lower device)
N) storage means and M-1 of the segments are exchanging data with a lower device, and when further exchanging data with another lower device, among the segments. And dividing means for dividing the remaining one of the two, and data is exchanged between the segment divided by the dividing means and the other lower device.

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

FIG. 1 is a block diagram showing a configuration of a system including a magnetic tape control device which is an embodiment of a control device with buffer storage according to the present invention, and shows a case where a lower device is a magnetic tape device.

In the figure, a magnetic tape processing device 1 is connected to a host device 2 and a plurality of magnetic tape devices 3. For the sake of explanation, the magnetic tape device 3 is MTU1, MTU2, MT in the following order.
Shown as U3, MTU4, MTU5, MTU6.

The higher-level device connection unit 11 controls the interface when performing command transfer, data transfer, and status transfer with the higher-level device 2.

The microprocessor 12 controls the overall operation of the magnetic tape controller 1. The recording / reproducing control unit 13 controls operation of the magnetic tape device 3, control of data transfer,
Error detection is performed. The magnetic tape device 3
Data is written to and read from a magnetic tape medium (not shown).

The buffer memory 15 temporarily stores the WRITE data sent from the host device 2 or the READ data read from the magnetic tape device, and adjusts the difference in data processing speed between the host device 2 and the magnetic tape device 3 and the data transfer timing. It is provided for taking. The buffer memory 15 is composed of a plurality of segments, and each segment has a continuous address. For the sake of explanation, each segment is SEG
Shown as 1, SEG2, SEG3, and SEG4.

The buffer memory control unit 14 selects and allocates a segment from which data should be actually written or data should be read out from a plurality of segments of the buffer memory 15 according to an instruction from the microprocessor 12.

The buffer storage division flag 16 is a flag set by the microprocessor 12 when the segment of the buffer storage 15 is divided, and is present corresponding to each segment. When the buffer division flag 16 is set, the continuity of the address of the segment corresponding to the flag is lost.

In such a configuration, the host device 2 to the host device connection unit
The instructions and data sent via 11 are analyzed by the microprocessor 12. If the analyzed command is a READ / WRITE command for the magnetic tape unit MTU1, buffer storage 15
If there are multiple segments available, allocate unused segments to MTU1.

Now, assume that SEG1 is assigned to MTU1. Then, in the case of the WRITE instruction, the microprocessor 12 subsequently instructs the upper device connection unit 11 and the buffer storage control unit 14 to transfer the WRITE data from the upper device 2 to the SEG1.

Further, in the case of a READ command, it instructs the recording / reproduction control unit 13 and the buffer storage control unit 14 to transfer READ data from MTU1 to SEG1. After that, when a READ / WRITE command is issued from the host device 2 to another magnetic tape device, the microprocessor 12
Similarly, if a plurality of segments are available in the buffer memory 15, an unused segment is allocated to the magnetic tape device and data transfer is started.

Similarly, when allocation or data transfer is performed and the number of empty segments becomes one, the microprocessor 12 does not allocate buffer storage, and the magnetic tape medium is loaded and READ / WRITE is possible (READY) on the magnetic tape medium. Check how many magnetic tape units are active. If there is only one magnetic tape device that meets the condition, the remaining segments are similarly assigned to the magnetic tape device.

Further, when there are two or more magnetic tape devices that meet the above conditions, it is determined that a READ / WRITE command may be issued to those devices, and the microprocessor 12
Allocates half of the remaining segment to the next magnetic tape unit.

Now, assuming that SEG4 of the buffer memory 15 is assigned to the magnetic tape device MTU4, the microprocessor 12 is
Allocate to MTU4 an address lower than half the size of the storage area of, that is, lower than half. However, when the block length of the data block processed immediately before in the magnetic tape device MTU4 exceeds 1/2 of the size of the storage area of the segment of the buffer storage 15, the SEG4 is assigned to the MTU4 without being divided.

Then the segment of buffer store 15 is not allocated, and
A check method of the magnetic tape device in the READY state will be described with reference to FIG. In the figure, 12 is a microprocessor, 120 is a magnetic tape device status table, and 17
Is a buffer storage control table.

The magnetic tape device status table 120 is a table of flags indicating whether each magnetic tape device is in the READY state or the NOT READY state, and corresponds to each magnetic tape device. When the microprocessor 12 receives a report from the recording / reproducing control unit 13 that the state of an MTU has become READY, it sets the flag corresponding to that MTU in the magnetic tape device state table 120 to "1". Conversely, the MTU status is NOT
When it receives the report that it has become READY, it resets the flag corresponding to that MTU to "0".

The buffer storage control table 17 is a table used by the microprocessor 12 to manage the buffer storage 15,
It exists for each MTU. Further, the buffer storage control table 17 has two fields of a buffer storage allocation flag 171 and a final processing data length 172.

The buffer allocation flag 171 is set to "1" by the microprocessor when allocating the segment of the buffer to the MTU and reset to "0" when the allocation is released.

The final processed data length 172 always stores the data length of the currently processed block by overwriting. Therefore, the content of the final processed data length field remaining at the end indicates the data length of the block processed last (immediately before) in the MTU.

Therefore, if the number of MTUs in which the READY flag of the magnetic tape device status table is "1" and the buffer storage allocation flag 171 of the buffer storage control table 17 is "0" is counted, whether or not the above-described division processing is performed is performed. Will be able to judge.

When the segment is divided based on the result of the above judgment, the microprocessor 12 sets the buffer storage division flag 16 of the corresponding segment. When the lower address in the segment of the buffer memory 15 is written or read when the buffer division flag 16 is set and the address reaches the address of the division boundary, the buffer control unit 14 writes or reads. Returns the address to the start address.

Further, when writing or reading an upper address in the segment, if the address reaches the final address, the buffer storage control unit 14 returns the write or read address to the division boundary address of the segment.

For example, one of the segments of the buffer memory 15 is from 0000 (HEX) to FFFF (HE as shown in FIG. 3 (a).
In case of having 64KB address up to X), 0000 (HEX) to 7FFF (HEX) as shown in FIG.
Is the lower address, 8000 (HEX) to FFFF (HEX)
Is the higher address. As described above, SEG4 is divided into two segments and can be used.

When a READ / WRITE command is issued to another magnetic tape device after dividing the segment, the microprocessor 12 immediately assigns the higher address of the divided segment to the next magnetic tape device. This allows
The data transfer can be started immediately.

Furthermore, when the use of the undivided segment ends and the occupancy is released and the next allocation is made to the magnetic tape device,
If the segment is the last segment, the segment division processing is applied as described above. Therefore, when all the segments are divided, it is possible to store a maximum of twice as many data of the magnetic tape device as the number of the segments in the buffer memory 15.

Next, the procedure of segment division and allocation by the microprocessor will be described with reference to FIG.

First, the microprocessor determines whether the command from the host device is a READ command or a WRITE command (step 41). If the command is not the READ command or the WRITE command, the process ends (steps 41 → 42).

If the command is a READ command or a WRITE command, it is determined whether or not a buffer storage segment is assigned to the magnetic tape device associated with the command (steps 41 → 43). If the segment has already been assigned, the process ends (step 43 → 52).

On the other hand, if the segment is not assigned yet, it is judged whether the number of remaining segments is one, that is, the last segment (step 43 → 44). here,
If the number of remaining segments is not one, an unused segment is allocated to the magnetic tape device (step 45), the buffer storage allocation flag corresponding to that segment is set (step 46), and the processing ends. (Step
52).

If the number of remaining segments is one, that is, the last segment, it is determined whether the segment has been divided (steps 44 → 47). If the segment has already been divided, an unused one of the divided segments is assigned to the magnetic tape device (step 47).
(→ 45), the buffer storage allocation flag corresponding to the segment is set (step 46), and the process ends (step 52).

On the other hand, if the segment is not yet split,
This time, referring to the magnetic tape device status table and the buffer storage allocation flag, it is judged whether or not there is only one magnetic tape device in which the segment is not allocated in the READY state (steps 47 → 48). If it is one, the last segment is assigned to the magnetic tape device (steps 48 → 45), the buffer storage assignment flag corresponding to that segment is set (step 46), and the process ends (step 52).

If it is not one, the segment is divided and the buffer storage division flag is set (step 48 → 49). Then, the segment after the division is assigned to the magnetic tape device (step 50), the buffer storage assignment flag corresponding to the segment is set (step 46), and the process is terminated (step 52).

As described above, the number of segments to be divided can be dynamically changed from 1 to 2 times depending on the load applied to the magnetic tape device.
The situation where the AD / WRITE command is kept waiting is gone.

Although the case where the lower device is a magnetic tape device has been described in the present embodiment, the present invention is not limited to this, and it is apparent that the present invention can be applied to other devices such as a magnetic disk device and a floppy disk device. Is.

Further, although the case where each segment is divided into two has been described in the present embodiment, it is clear that the segment may be divided into three. In this case, the number of flags corresponding to each segment may be increased.

As described above, according to the present invention, in a control device with a buffer memory, the buffer memory is divided into segments and can be used, so that a larger number of magnetic tape devices than the number of segments of the buffer memory can be used. Buffer memory can be allocated to the recording / reproducing mechanism at the same time, which has the effect of reducing the time loss of the recording / reproducing command caused by waiting for the buffer memory to become empty.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration when the present invention is applied to a magnetic tape control device, FIG. 2 is a schematic diagram showing a check system for a magnetic tape device in a microprocessor, and FIG. 3 is a buffer storage segment. FIG. 4 is a flow chart showing the processing procedure of segment division and allocation by the microprocessor. Explanation of symbols of main parts 12 ... Microprocessor 15 ... Buffer memory 16 ... Buffer memory division flag

Claims (1)

(57) [Claims] 1. A control device with a buffer memory, which is connected to N lower devices, and is composed of M (2 ≦ M <N) segments for exchanging data with the N lower devices, respectively. Storage means and M-1 of the segments are exchanging data with a lower device, and the remaining one of the segments is divided when exchanging data with another lower device. And a dividing unit for performing data exchange between the segment divided by the dividing unit and the other lower-level device.