JPS58203561A - Controlling device of external storage - Google Patents

Abstract

PURPOSE:To separate a defective bus forcibly from an external storage controlling device to be coupled with plural CPUs through different data buses and to switch the controlling device to the other system by providing the controlling device with a bus fault checking means in each bus system independently. CONSTITUTION:Regarding that a CPU1 is a current system and a CPU2 is an auxiliary system, data are transferred between the CPU1 and an external storage device 13 through the external storage controlling device 24. When an error is detected by a parity check circuit 3 in the device 24, an error latch circuit 5 is set up. The output of the circuit 5 is sent to the CPU1 through a signal line 18 and the CPU1 recognizes the generation of a fault in the data bus system and returns a response signal through a signal line 19. As the result, the output of an AND circuit 8 is turned to ''0'', the AND condition of an AND circuit 10 is not satisfied and the external storage device 13 is separated from the CPU1. If the error is not recovered by retrial, a selecting circuit 7 turns a signal line 22 to ''0'' and a signal line 23 to ''1'', so that the condition of an AND circuit 11 is satisfied and the external storage device 13 is coupled with the CPU2.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention The present invention relates to an external storage control device in an electronic computer system, and more particularly to an external storage control device that easily performs system switching control in a redundant system ζ.

BACKGROUND OF THE INVENTION Today, electronic computer systems are required to have larger capacity and faster external storage devices, as well as higher system reliability. For this reason, most large-scale computer systems have system duplication, and even if one central processing unit fails and goes down, the entire system can be restored by switching to another central processing unit. Prevents you from going down.

On the other hand, a failure in an external storage device generally occurs in an area related to the job ζ when a single job is being executed, so although the job may be canceled, it is unlikely that the system will go down. .

Now, if a failure occurs in the central processing unit and it is necessary to switch to another system, the following steps are required.

(1) Disconnect the currently connected central processing unit and external storage control #c*.

(21) Connects the central processing unit of another thread and the external storage control unit.

Here, it is good if (1) can be separated, but if it is not possible, (2) cannot be combined. Therefore, even in a redundant system, system failure is inevitable if a failure makes it impossible to disconnect.

Therefore, in recent technology, in the event of a failure of the central processing unit, an independent line is provided to transmit the signal to the external storage controller (two-speed). However, failures in data bus systems such as cable connections, drivers, and receivers cannot be detected by the central processing unit, and the parts controlled by external storage devices are not affected at all. A non-separable state occurs even though there are no problems.This is due to the following reasons.

(1) Even if you try to perform disconnection by issuing a programmatic disconnection command from the central processing unit,
Due to the nature of the failure, communication to the external storage controller is impossible.

(2) Since it is not possible to isolate whether the failure is related to the external storage control device or the external storage device, it is virtually impossible to treat the system.

As described above, even in duplex systems, there was a very serious problem in the past in that if a failure occurred in the data bus thread, the system would go down.

OBJECTS OF THE INVENTION An object of the present invention is to provide an external storage control device that can be disconnected even if a failure occurs in the data bus system and switch to another system.

The present invention provides an independent check function for failures in the external storage control device (= data bus system), and when a failure occurs, it sends a notification to that effect to the central processing unit, and the connection state is determined by a response signal. This forcibly disconnects the system, thereby making it easier to switch to another system.

Embodiment of the Invention The figure shows an embodiment of the invention, and the area within the broken line % indicates an external storage control device according to the invention. The external storage control circuit consists of an external storage control circuit 12, a selection circuit 7 that controls which of the central processing units 1 and 2 is selected, and a group of associated circuits.

Now, the central processing unit ll side is the current system, central processing unit 2.
It is assumed that the external storage device 2I41I is connected to the central processing unit 1. In this case, the selection circuit 7 sets the signal line 22 to °l'' and the signal line to 101.

As a result, the AND condition of the AND circuit is satisfied (as described later, the output of the AND circuit 8 is normally 11"), and the connection state of the data bus 14Ib1 with the central processing unit 1 is determined. This connection In the state, the central processing unit 1 and the external storage device 18 are connected through the external storage device 18.
Data transfer via data buses 14 and 16 is performed between the two.

Now, data sent from the external storage device or central processing unit 1 is manually input to the parity check circuit 8 via the data bus 14 to perform a parity check. When the parity check circuit 8 detects an error, the error latch circuit 5
Set. The output of the error latch circuit 5 is the signal line 18
The signal is then sent to the central processing unit l, which recognizes that a failure has occurred in the data bus system and sends back a response signal through the signal line 19. the result,
Since the output of the AND circuit 8 becomes O'' (the AND circuit 8
1 in the output of. '' indicates an inverter), the AND condition of the AND circuit IO no longer holds, and the disconnection from the central processing unit 1 is achieved. Note that the error latch circuit 5 is
It is reset by a response signal from the central processing unit 1. This makes it possible to try using only one system without changing systems. If the error is not recovered even after retrying, the selection circuit 7 sets the signal line 22 to @θ'' and instead sets the AND circuit 11 to the two-signal llm28 to "l", and connects it to the central processing unit 2. .

In the conventional technology, parity check is performed using external storage Th.
Since this was done in front of the 1J111 circuit 12, it was not possible to determine the location of the failure, and therefore it was impossible to switch the yarn.

Father, even if it is installed independently, if the central processing unit cannot recognize it, it will still not be possible to switch. In contrast, in the present invention, switching is made possible by providing a parity check independently for each system and by providing a response line independent of the central processing unit.

Although the case where the external storage control device 24 is coupled to the central processing unit 1 has been described above, the operation is exactly the same when the external storage control device 24 is coupled to the central processing unit [2].

Effects of the Invention According to the present invention, even if a failure occurs in the data bus system, the thread can be cut off reliably and easily, so that the thread can be cut properly. This prevents the system from going down even if the above-mentioned failure occurs, increases system reliability, and has the effect of reducing damage when a failure occurs.

[Brief explanation of the drawing]

The figure is a configuration diagram of an embodiment of an external storage control device according to the present invention. 1, 2... central processing itt, 8, 4... parity check 1':

Claims (1)

[Claims] (1) In an external storage control device that is connected to a plurality of central processing units through different data bus systems and controls data transfer between the plurality of central processing units and an external storage device, a failure in the data bus system ;= An independent check means is provided for each thread, and when a failure persists, it is connected to the central processing #cr1t connected to the data bus system,
An external storage control device whose purpose is to forcibly disconnect the connection state of the data bus system by a response signal from the central processing unit.