System and method for operating a SCSI bus with redundant SCSI adaptors

• US 6,735,715 B1
• Filed: 04/13/2000
• Issued: 05/11/2004
• Est. Priority Date: 04/13/2000
• Status: Expired due to Term

• Current Assignee: Stratus Technologies Ireland Ltd. (Stratus Technologies Bermuda Holdings Ltd.)
• Original Assignee: Stratus Technologies Bermuda Ltd. (Stratus Technologies Bermuda Holdings Ltd.)
• Inventors: Graham, Simon P.
• Primary Examiner(s): Beausoliel, Robert
• Assistant Examiner(s): CHU, GABRIEL L
• Application Number:
  US09/548,530
• Time in Patent Office: 1,489 Days
• Field of Search: 714/43, 714/56, 714/2, 714/3, 714/9, 710/100, 710/120, 710/119, 710/312, 710/311, 710/306
• US Class Current: 714/5.11
• CPC Class Codes: G06F 11/2005 using redundant communication controllers
• CPC Class Codes: G06F 11/2007 using redundant communication media

Abstract

A computer system includes a port duplex driver (PDD) that creates a “virtual SCSI adaptor,” to control the operations of one or more redundant SCSI adaptors. During boot-up operations or when the status of a device on a SCSI bus changes, the PDD identifies the virtual SCSI adaptor as the only adaptor that provides access to particular storage devices on the SCSI bus. System components then direct data transfer operations through the virtual SCSI adaptor to the storage devices. The PDD intercepts commands that are directed through the virtual SCSI adaptor, and redirects the commands to a selected one of the actual SCSI adaptors. The selected SCSI adaptor then operates in a conventional manner, to translate the generic commands from the system components to device-specific commands for the storage devices on the SCSI bus. If the selected SCSI adaptor fails, the PDD redirects the data transfer operations instead through one of the redundant SCSI adaptors. The failure does not affect the remainder of the system, which continues to conduct data transfer operations through the virtual SCSI adaptor.

Claims

1. A computer system including:

A. one or more storage devices connected to a first bus;

B. one or more system components that connect to a second bus and communicate with the storage devices;

C. one or more bus adaptors for transferring communications to and from the second bus and the storage devices on the first bus;

D. a port duplex driver for mapping one or more communications paths to the storage devices through the one or more bus adaptors to a communication path through a virtual bus adaptor,

E. object means for assigning to each storage device on the first bus a device object that corresponds to the communications path through the virtual bus adaptor, the object means informing the system components of the assigned device objects; and

F. the port duplex driver further re-directing to a selected one of the bus adaptors communications from the system components that include the assigned device objects.

2. The computer system of claim 1 further comprising:

a. a mini-port driver that identifies the storage devices as belonging to a given special class of device, and

b. a plug and play manager that associates the given special class of device with the port duplex driver.

3. The computer system of claim 1 wherein the first bus is a SCSI bus and the second bus is a system I/O bus.

4. The computer system of claim 3 wherein the system I/O bus is a PCI bus.

5. The computer system of claim 1 wherein the port duplex driver changes the selection of the bus adaptor from a previously selected bus adaptor that has failed to an operative bus adaptor.

6. The computer system of claim 5 wherein the port duplex driver re-issues to the operative bus adaptor the communications that were directed to the failed bus adaptor after the failure.

7. The computer system of claim 1 further comprising:

G. additional storage devices connected to another first bus,

H. the one or more bus adaptors are dual ported, and

I. the port duplex driver selects one bus adaptor for use on one first bus and a different bus adaptor for use on the other first bus.

8. A method of operating a computer system, the method comprising the steps of:

A. determining that one or more storage devices are accessible over a first communications bus through one or more bus adaptors;

B. mapping the one or more bus adaptors to a virtual bus adaptor and presenting to system components that communicate with the storage devices a communication path through the virtual bus adaptor to the storage devices;

C. assigning to each storage device on the first communications bus a device object that corresponds to the communications path through the virtual bus adaptor;

D. informing the system components of the assigned device object, and

E. re-directing to a selected one of the bus adaptors the communications that are directed through the virtual bus adaptor to the storage devices.

9. The method of claim 8 wherein the step of determining that the one or more storage devices are accessible over the first communication bus includes:

i. sending queries to the storage devices through each of the one or more bus adaptors and receiving responses from the storage devices through each of the one or more bus adaptors,

ii. identifying the storage devices as devices that are controlled by a port duplex driver,

iii. reporting by the port duplex driver that the storage devices are accessible through the virtual bus adaptor.

10.The method of claim 9 wherein the step of reporting by the port duplex driver includes

a. determining that the one or more bus adaptors provide redundant paths to the storage devices, and

b. mapping the bus adaptors that provide the redundant path to the same virtual bus adaptor.

12. The method of claim 9 wherein the step of mapping further includes mapping a newly added bus adaptor to the virtual bus adaptor if the newly added bus adaptor provides a redundant path to the storage devices.

10. The method of claim 10 wherein the step of determining redundant paths further includes

c. identifying the storage devices as special devices that are accessible through each of the bus adaptors;

and

d. associating the special devices with the port duplex driver.

11. The method of claim 11 wherein the port duplex driver:

e. in the step of reporting further includes reporting the virtual bus adaptor and the storage devices as devices to which the system assigns device objects, and

f. in the step of re-directing further includes re-directing to a selected bus adaptor the communications that include the device objects that are assigned to the storage devices.