JPH04177552A - Scsi device - Google Patents

Abstract

PURPOSE:To increase the number of devices which can be connected by handling a small computer system interface(SCSi) device to be increased, as a logical unit. CONSTITUTION:The address designation in the case an initiator 1 (SCSi device 17) communicates with a target 2 (SCSi device 41) is executed (LUN1 of an address 3) so as to indicate an address on an external SCSi bus B1 and a logical unit LUN1 being thereunder. An interface controller 30 which receives this address designation executes an address conversion so as to designate LUN0 of an address 1 by an internal SCSi bus B2. The address 1 of this internal SCSi bus B2 is the target 2, and the LUN0 is a logical unit being thereunder. In such a state, when the target 2 responds to the LUN0 of the address 1, a communication path is secured to the initiator 1. In such a way, the number of devices which can be connected to the SCSi bus is increased exceeding restrictions of the address.

Description

[Detailed Description of the Invention] [Summary] In an SCSi device that connects a plurality of host computers and peripheral devices via a bus, the number of devices that can be connected to the bus can be increased beyond the address constraints (by avoiding scraping). a first SCSi bus capable of connecting a plurality of initiator SCSi devices distinguished by limited addresses;
an interface controller connected in place of the initiator SCSi device; a second SCSi bus arbitrating between the first SCSi bus; and a plurality of interface controllers connected to the second SCSi bus. The target SCSi device is configured to include a target SCSi device.

[Industrial application field]

The present invention relates to an SCSi (Small Computer System Interface) device having a two-layered bus structure.

[Conventional technology]

SCS as one of the computer system interfaces
There is a standard called i, and it is expected that it will become the standard for future interfaces. In this SCSi standard, devices on the bus are distinguished by unique addresses, and any devices can communicate with each other.

FIG. 2 shows an example of a system configuration according to the SCSi standard. A plurality of SCSi devices 10 to 17 are connected to the common SCSi bus B1, and these devices are distinguished by addresses 0 to 7. One SCSi device includes drives 20, 21, 22 . . . called logical units.・・・・・・
Up to 7 devices can be connected. Taking a tape storage device as an example, this logical unit would be a drive that records/plays back on tape.

[Invention or problem to be solved]

The SCSi standard bus B1 shown in FIG. 2 consists of eight data buses and multiple control lines including a line that distinguishes whether the data bus is used for data or for addresses. 1 of 8 data buses
It is stipulated that the book be at the opposite level to the remaining seven books.

Therefore, in this SCSi standard, only eight SCSi devices can be connected at most due to address restrictions. For this reason, even if a user attempts to construct a system using nine or more SCSi devices, there is a problem in that the system cannot be realized.

The present invention makes it possible to increase the number of connectable denominations beyond address constraints by treating additional SCSi devices as logical units.

[Means to solve the problem]

The SCSi device of the present invention includes a first SCSi bus capable of connecting a plurality of initiator SCSi devices distinguished by limited addresses;
an interface controller connected on behalf of the device; a second SCSi bus arbitrating between the controller and the first SCSi bus;
It is characterized by comprising a plurality of target SCSi devices connected to a CSi bus.

[Effect]

A target S has a hierarchical structure of a first SCSi bus and a second SCSi bus, and is connected to the second SCSi bus.
If the CSi device is treated as an initiator SCSi device or a logical unit connected to the first SCSi bus, this initiator SCSi device can be added without occupying an address on the first 5C8i bus.

〔Example〕

FIG. 1 is a system configuration diagram showing an embodiment of the present invention, and B1
is the external (first) SCSi bus, B2 is the internal (second)
SCSi bus, 11 is an initiator SCSi device that becomes a host computer (however, i = 0 to 7), 30
is the interface controller, and 4j is the target SCSi device as a peripheral device (j = 0 to 6)
It is.

Up to eight initiator SCSi devices li, distinguished by addresses 0 to 7, are connected to the external SCSi bus B1. In this system, for example, address 3
Interface controller 30 with the SCSi device
Instead, if an internal SCSi bus B2 is provided under it,
A maximum of seven target 5C8i devices 4j can be connected to this internal 5C81 bus B2. Internal S
Since the CSi bus B2 also has eight data buses or the interface controller 30 is connected thereto as one SCSi device, there are a maximum of seven target SC8i devices 4j.

SCSi device for target 40, 41°...
... each has one built-in logical unit and internal SCS
Address 0. on i-bus B2. Address 1゜・・・・・・
・, address 6 are distinguished. In this case, the interface controller 30 becomes the initiator 1 of the address. However, this is for the target SCSi device 4j, and is address 3 on the external SCSi bus Bl.

With such a two-layer bus structure, addressing from the initiator to the target is as follows. for example,
When communicating with initiator 1 (SCSi device 17) or target 2 (SCSi device 41), address specification is made to point to address 3 on external SCSi bus Bl and logical unit LUN1 under it (LUNI of address 3) . The interface controller 30 that has received this address converts the address so that the LUNO at address l is specified using the internal SCSi path B2.

Address 1 of internal SCSi bus B2 is target 2, and LNNO is the logical unit under it. When target 2 responds to the LUNO at address l, a communication path is established with initiator 1.

The process of selecting a target from the interface controller 30 is subdivided into an arbitration phase for acquiring the internal SCSi bus B2 and a selection phase for selecting a device.

In the arbitration phase, the controller 30 can act as address 7 on the internal bus, or in the selection phase, it can use address 6 of the initiator (SCSi device 16 in this case) accessed from the external bus. By doing this, the cause of the trouble that occurred at the target (41 in this case) can be
The target (41) can hold each initiator (16) communicating at that time.

〔Effect of the invention〕

As described above, the present invention has the advantage that the number of devices that can be connected to the SCSi bus can be increased beyond address constraints.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of the present invention, and FIG. 2 is a conventional system configuration diagram. In the figure, B1 is an external SCSi bus, B2 is an internal SCSi bus, 11 is an initiator SCSi device, 30 is an interface controller, and 4j is a target SCS
It is an i-device. Applicant Fujitsu Ten Ltd.

Claims (1)

[Claims] 1. A first SCSi bus capable of connecting a plurality of initiator SCSi devices distinguished by limited addresses; an interface controller connected in place of the initiator SCSi device; An SCSi device comprising: a second SCSi bus that arbitrates with the first SCSi bus; and a plurality of target SCSi devices connected to the second SCSi bus.