JPH04364514A - Dual-port disk controller - Google Patents

Abstract

PURPOSE:To put the SCSI bus between disk controllers and disk devices in efficient operation and to prevent resetting conditions of one disk controller from exerting adverse influence upon the other disk controller. CONSTITUTION:When the disk controller A2a sends a request to reserve the disk device #0 thorugh a controller A reservation I/F circuit 31a so as to access the disk device #0 and disk device #1, a SCSI bus switching circuit 33 and a disk SCSI data circuit 34 are informed that the device #0 is reserved by the controller A. The busy signal and select signal on the SCSI bus of the device #0 are shown to a controller A SCSI busy sequencer circuit 36a and a controller A SCSI select sequencer circuit 35a and the circuit 33 shows the busy signal and select signal of the controller A to the device #0.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shared controller for a disk sharing mechanism connected to a minicomputer.

0002

2. Description of the Related Art FIG. 3 shows an example of a dual port configuration using a multi-initiator, which is a standard function of a SCSI bus. In the figure, 1 is a disk controller, 2 is a disk device, and 3 is a SCSI bus. 5, Figure 6, Figure 7
is an attached diagram for explaining the operation.

Next, the operation will be explained. In FIG. 4, when the disk controller 1 accesses the disk device 2, the command is defined as a standard SCSI bus command for exclusive control of the disk device between the two disk controllers. Issue reserve and release commands. FIG. 5 shows a comparison of the situation on the SCSI bus at this time with that in a case where there is no multi-initiator.

The upper part of FIG. 5 shows the state of command execution and data transfer on the SCSI bus in a single initiator and the lower part in a multi-initiator. As shown in FIG. 5, in the multi-initiator, in order to issue reserve and release commands, an additional processing time corresponding to the processing time of this command is required compared to the single initiator.

The throughput seen from one CPU will be explained with reference to FIG. The upper part of FIG. 6 shows the command execution/data transfer state on the SCSI bus when the right to use the bus can be acquired alternately between CPUs in a single initiator and the lower part in a multi-initiator. As shown in FIG. 6, in a multi-initiator, one bus is shared between CPUs, and when the CPUs are using the bus, disk access is made to wait, resulting in a decrease in throughput.

The interference conditions between CPUs will be explained with reference to FIG. Since the SCSI bus supports disk connect conditions as a standard function, there are situations in which the disk device receives only a reserve command and releases the SCSI bus. FIG. 7 shows a state in which two disk controllers each maintain logical connections with two disk devices using this function. In this state, if one disk controller generates an initialization request due to an error condition of the disk device and drives the reset signal on the SCSI bus, the reset drive on the SCSI bus is
Since all disk devices connected to the SI bus are prompted to be initialized, the disk device that was logically connected to the other disk controller will also be initialized.

As a result, in the disk controller that does not issue the reset, a logically connected disk device may not return a response, resulting in an error. In this multi-initiator configuration, the reset drive of one disk controller causes an error in the other disk controller.

[0008]

[Problem to be solved by the invention] SCS according to prior art
Since the operation of the I-bus multi-initiator configuration was as described above, there were the following problems. (1) In order to perform exclusive control of disk devices between disk controllers, it is necessary to execute reserve and release commands before and after executing read or write commands to the disk device. This required 6 msec, which is 20% of the average access time of about 30 msec required to read or write one block of the device, and was a factor in reducing the access time.

(2) Since the configuration is such that two disk controllers share one SCSI bus, even if separate disks are accessed between the disk controllers, one disk controller uses the SCSI bus. In the middle, disk access from the other disk controller had to wait, which caused the throughput related to disk access from one CPU to drop by more than half.

(3) Since the configuration is such that one SCSI bus is shared by two disk controllers, if one disk controller issues a reset to the SCSI bus, the other disk controller will check the logical connection at this time. If there was a disk device that had been previously used, that disk device would also be forced to be initialized, resulting in an error.

[0011] The present invention aims to solve these problems by efficiently operating the SCSI bus between a disk controller and a disk device, and by preventing the reset condition of one disk controller from affecting the other disk controller. The aim is to obtain a dual-port disk controller that does not give up.

0012

[Means for Solving the Problems] A dual disk control device according to the first invention is a dual port disk control device having a function of allowing two SCSI control devices to share a plurality of disk devices with SCSI interface specifications. , the SCSI control device monitors the busy signal output for disk occupancy, and when the busy signal is confirmed in the SCSI bus arbitration phase,
It generates its own busy signal according to the SCSI arbitration protocol specifications and also uses the SCSI bus ID.
It is equipped with a SCSI busy sequencer corresponding to each SCSI control device that drives the SCSI bus data line corresponding to the number.

[0013] Furthermore, the dual disk control device according to the second aspect of the present invention provides SCSI bus control for one SCSI control device and the plurality of disk devices in the selection phase or reselection phase of the SCSI bus after arbitration. Generates a select signal according to arbitration protocol regulations, and
It is equipped with a SCSI bus select sequencer corresponding to each SCSI control device that drives the SCSI bus data line corresponding to the bus ID number.

Further, the dual disk control device according to the third invention is provided with an SCSI bus switching circuit, so that the two SCSI control devices can simultaneously connect to a plurality of disk devices and the SCSI bus switching circuit.
This allows exclusive connection between SI control devices.

Further, the dual disk control device according to the fourth invention provides an exclusive control bus between the SCSI control devices, and also includes a disk device reserve circuit for receiving this bus. This is to exclusively specify one SCSI disk device.

[0016]

[Operation] The SCSI busy sequencer in this first invention performs
By detecting the SCSI bus on which the arbitration phase has started, a busy signal is generated and the SCSI bus
Output to a SCSI bus other than the I bus.

[0017] The SCSI selection sequencer in this second invention identifies the device that won the arbitration by detecting that the selection or reselection phase has started among all logically connected SCSIs. , SCS to which the device is connected
The state of the I bus is reflected on SCSI buses other than the SCSI bus.

[0018] The SCSI bus switching circuit in this third invention allows only the SCSI bus instructed by the SCSI control device to be connected to the SC that is physically connected to the SCSI control device.
Connect logically to the SI bus.

[0019] The reserve circuit in this fourth invention is as follows:
Reserve information of all devices connected to the SCSI bus other than the SCSI control device is maintained and managed.

[0020]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a fixed disk device, 2a is a disk controller A that controls the fixed disk device 1,
2b is another disk controller B that controls the fixed disk device 1; 3 is a dual-port disk controller; 4 is a dual-port disk controller;
a is a SCSI bus that connects the fixed disk device 1 and the dual-port disk controller 3; 4b is a SCSI bus that connects the dual-port disk controller 3 and the disk controller 2a; and 4c is a SCSI bus that connects the dual-port disk controller 3 and the disk controller 2b. SCSI to connect
It's a bus.

Further, in FIG. 2, 31a is a controller A that serves as an interface for controlling the disk controller A 2a to reserve the disk device 1.
Reserve I/F, 31b is disk controller B
controller B reserve I/F, which serves as an interface for 2b to perform control for reserving the disk device 1;
32 is a reserve controller that manages the reserve of the disk device 1; 33 is a SCSI that switches the SCSI bus between the disk device 1 and the dual port disk controller 3;
The bus switching circuit 34 is a disk SCSI data circuit that changes the output destination of the SCSI signal from the SCSI bus switching circuit 33 depending on the reserve state of the disk device 1.

A controller A SCSI busy sequencer 36 monitors the SCSI busy signal of the disk controller A 2a and the disk device 1 reserved by it, and 35 monitors the SCSI select signal of the disk controller B 2b and the disk device 1 reserved by it. controller A SCSI select sequencer, 36 is disk controller B
2b and the SCSI of disk device 1 reserved by this
Controller B that monitors the select signal of SCSI
It is a select sequencer.

37a is the disk controller A 2a
A controller that outputs the SCSI signal of A SC to the SCSI bus switching circuit 33 according to the SCSI phase.
SI data out circuit, 37b is a controller B SCSI data out circuit that outputs the SCSI signal of disk controller A 2b to the SCSI bus switching circuit 33 according to the SCSI phase, and 38a is a controller A SCSI I that interfaces with the SCSI bus of disk controller A. /F circuit, 38
b is a controller B SCSI I/F circuit that interfaces the disk controller B's SCSI bus.

Next, the operation will be explained. When the disk controller A 2a accesses the disk device #0 and the disk device #1, first, it issues a reservation request for the disk device #0 to the reserve controller circuit 32 through the controller A reserve I/F circuit 31a. The reserve controller circuit 32 turns on the occupancy flag of disk device #0 if the disk device is not occupied. In addition, the reserve controller 32
It notifies the SCSI bus switcher (switching circuit) 33 and the disk SCSI data circuit 34 that 0 is reserved in the disk controller A 2a. In response, the disk SCSI data circuit 34 shows the busy signal and select signal on the SCSI bus 4b of disk device #0 to the controller A SCSI busy controller circuit 36a and the controller ASCSI select sequencer circuit 35a, and the SCSI bus switching circuit 33 makes the busy signal and select signal of disk controller A 2a visible to disk device #0.

Next, a request to reserve disk device #1 is issued to the reserve controller circuit 32 through the controller A reserve I/F circuit 31a. The reserve controller circuit 32 turns on the occupancy flag of disk device #1 if the disk device is not occupied. Additionally, the reserve controller circuit 32 informs S that disk device #1 has been reserved by disk controller A 2a.
The information is transmitted to the CSI bus switching circuit 33 and the disk SCSI data circuit 34. In response to this, Disk S
The CSI data circuit 34 shows the busy signal and select signal on the SCSI bus 4a of disk device #1 and disk device #0 to the controller A SCSI busy sequencer circuit 36a and the controller A SCSI select sequencer 35a,
3 makes the busy signal and select signal of disk controller A 2a visible to disk device #1 and disk device #0.

The disk controller A 2a informs the controller A reserve I/
After checking through the F circuit 31a, the controller A S
Disk access from CSI circuit 38a to SCS
I will start in accordance with the terms and conditions. At this time, controller A
The SCSI busy sequencer circuit 36a monitors busy signals from the disk controller A 2a, disk device #0, and disk device #1.

When the disk controller A 2a outputs a busy signal for starting artvilation and one data signal corresponding to its own ID, the controller A
The SCSI busy sequencer circuit 36a generates a busy signal by itself and outputs it to the SCSI bus switching circuit 33. The SCSI bus switching circuit 33 switches this to disk device #.
0 and output only to disk device #1. In addition, one of the data signals corresponding to the own ID of disk controller A 2a is shown to disk device #0 and disk device #1,
One data signal corresponding to the own ID of disk device #0 is shown to disk controller A2a and disk device #1, and one data signal corresponding to the own ID of disk device #1 is shown to disk controller A and disk device #1. Make it look like 0.

At this time, the disk controller A 2
A, disk device #0, and disk device #1 operate as if they were one unit without being aware that the SCSI bus was separated.
Artvilation can be performed as if only the disk controller A 2a, disk device #0, and disk device #1 were connected to the SCSI bus of the book.

If the disk controller A 2a wins the artvilation, then the disk controller A 2a sends the select signal, one of the data signals corresponding to its own ID, and the I of the disk device to be selected.
One data signal corresponding to D is output. The controller A SCSI busy sequencer circuit 36a that detected the select signal output stops outputting the busy signal it generated, and instead sends the busy signal of the device that won the artvilation, that is, the disk controller A 2a, to the SCSI busy sequencer circuit 36a.
The signal is passed to the CSI bus switching circuit 33.

At the same time, the controller A S
When the CSI busy sequencer circuit 36a detects the select signal output, it generates a select signal by itself and outputs it to the controller A SCSI I/ and the SCSI bus switching circuit 33. Controller ASCSI I
/F 38a and the SCSI bus switching circuit 33 output the generated select signals to the disk controller A 2a and the disk device, respectively. It also outputs data signals according to the direction of I/O signals on the SCSI bus. That is, the data signal of disk controller A 2a is shown to disk device #0 and disk device #1.

Disk controller A 2a turns off the busy signal after a time specified by SCSI after issuing the select signal.
When the SCSI busy sequencer circuit 36a detects the SCSI busy sequencer circuit 36a, it sends the busy signal of the disk controller A 2a to the SC
The flow to the SI bus switching circuit 33 is stopped. After stopping for a while, the busy signal of the disk device to be selected is shown to the disk controller A 2a and other disk devices. If the disk device you are trying to select is disk device #0, the busy signal of disk device #0 is sent to disk controller A 2a and disk device #1.
Show it to.

After this, disk device #0 outputs a busy signal in order to respond to the selection. When the disk controller A 2a detects the output of the Vichy signal, it learns that the selection has been completed and stops outputting the select signal that has been output. When detecting that the output of the select signal has stopped, the controller A SCSI select sequencer 35a stops outputting the generated select signal. After that, signals output only by the disk controller will be shown from disk controller A 2a to disk device #0, signals that only the disk device will be outputted will be shown from disk device #0 to disk controller A 2a, and SCSI
Those by phase on the bus control direction by I/O signals.

If disk device #0 does not respond to the select for some reason and does not output a busy signal within the time specified by SCSI, it will know that it has failed to select disk controller A2a and will stop outputting the select signal. . In this case, controller A SCSI
Busy sequencer circuit 36a and controller A SC
The SI select sequencer circuit 35a returns to the initial state,
Controller A SCSI busy sequencer circuit 36a begins monitoring the busy signal.

The above series of operations is performed by disk controller B.
The disk controller A 2a and the disk controller B 2b can operate in parallel if there is no disk device contention. If a conflict occurs, the disk device is occupied by the disk controller that made the reservation first, and the disk controller that could not make the reservation during that time is forced to wait only for access to that disk device. Processing for the reserved disk controller is completed, and the disk controller is set to controller A.
After releasing the reservation through the reserve I/F circuit 31a, the disk controller that has been kept waiting can reserve the disk device.

Example 2. Further, in the above embodiment, the case of a disk device and a disk controller has been described, but any device may be used as long as it is a SCSI interface device and its controller, and the same effects as in the above embodiment can be obtained. Furthermore, in the above embodiment, the case where there are two disk controllers has been explained, but if controller A SCSI sequencer circuits and controller A SCSI sequencer circuits corresponding to the number of controllers are provided, the same effect as in the above embodiment can be obtained. play.

[0036]

As described above, according to the first invention, since the SCSI busy sequencer generates the busy signal on the divided SCSI bus in a pseudo manner and in accordance with the SCSI regulations, This has the effect of synchronizing the arbitration of devices and controllers connected on the bus.

Further, according to the second invention, since the select signal on the divided SCSI bus is generated in a pseudo SCSI selection sequencer and in accordance with the SCSI regulations, the selection signals on the divided SCSI buses are generated in a pseudo manner and in accordance with the SCSI regulations. This has the effect of allowing individual devices to correctly recognize the arbitration results of devices and controllers.

Furthermore, according to the third invention, all the signals on the divided SCSI bus are shown to the devices and controllers connected to the divided SCSI bus individually in accordance with the SCSI phase. This has the effect of allowing the device to see the SCSI bus as one SCSI bus.

Further, according to the fourth invention, since the reserve circuit is provided in terms of hardware, exclusive control of the device can be executed at high speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a dual port disk control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the hardware configuration of a dual port disk control device according to an embodiment of the present invention.

FIG. 3 is a block diagram showing the configuration of a conventional dual port disk control device.

FIG. 4 is a block diagram showing the operation of a conventional dual port disk control device.

FIG. 5 is a time chart showing the command execution state of a conventional dual port disk control device.

FIG. 6 is a time chart showing the throughput state of a conventional dual port disk control device.

[Figure 7] CP of conventional dual port disk controller
It is a block diagram showing interference conditions between U.

[Explanation of symbols]

1 Disk device 2a Disk controller A2b
Disk controller B3 Dual port disk control device 4a-4b SCSI
Bus 32 Reserve controller 33
SCSI bus switching circuit 35a controller A
Select sequencer 35b Controller B Select sequencer 36a Controller A
SCSI busy sequencer 36b Controller B SCSI busy sequencer

Claims (4)

[Claims] Claim 1: The above-mentioned SCSI controller is installed in a dual-port disk controller having a function of allowing two SCSI controllers to share a plurality of disk devices with SCSI interface specifications.
The CSI controller monitors the busy signal output for disk occupancy, and when the busy signal is confirmed during the SCSI bus arbitration phase, it generates a unique busy signal according to the SCSI arbitration protocol regulations and also outputs the SCSI bus ID. A dual port disk control device comprising a SCSI busy sequencer corresponding to each SCSI control device that drives a SCSI bus data line corresponding to a number. 2. In the SCSI bus selection phase or reselection phase after arbitration, a select signal is generated for one SCSI control device and the plurality of disk devices according to SCSI bus arbitration protocol regulations, and the SCSI
2. The dual port disk control device according to claim 1, further comprising a SCSI bus select sequencer corresponding to each SCSI control device that drives a SCSI bus data line corresponding to a bus ID number. [Claim 3] A SCSI bus switching circuit is provided so that two SCSI control devices can simultaneously connect multiple disk devices and SC
3. The dual port disk control device according to claim 1, wherein exclusive connection is possible between SI control devices. 4. An exclusive control bus is provided between the SCSI control devices, and a disk device reserve circuit is provided to receive this bus, so that up to seven SCSI disk devices can be exclusively designated between two CPUs. A dual port disk control device according to any one of claims 1 to 3.