Fiber channel arbitrated loop dynamic loop sizing

• US 6,504,817 B2
• Filed: 03/31/1997
• Issued: 01/07/2003
• Est. Priority Date: 03/31/1997
• Status: Expired due to Term

• Current Assignee: Comcast IP Holdings I LLC (Comcast Corporation)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Oldfield, Barry J., Mejia, Robert G.
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): TRINH, DUNG N
• Application Number:
  US08/828,985
• Publication Number:
  US 20020012342A1
• Time in Patent Office: 2,108 Days
• Field of Search: 370/221, 370/222, 370/223, 370/224, 370/225, 370/405, 370/227, 370/228, 370/249, 370/461, 370/216, 370/217, 714/4
• US Class Current: 370/217
• CPC Class Codes: H04L 12/433 with asynchronous transmission, e.g. token ring, register insertion

Abstract

In a Fiber Channel Arbitrated Loop communications architecture, dynamic loop sizing includes selectively bypassing operational device ports in the loop in order to minimize overhead associated with loop size. In redundant systems with multiple loops, the system is optimized by judicious distribution of the bypassed ports among the loops. Redundancy is at no point reduced. By bypassing unused or unneeded ports off of a loop, the round trip delay of the loop is appreciably shortened. By minimizing the round trip delay, arbitration overhead and access latency is reduced, and loop bandwidth and overall performance is improved. Dynamic load sharing balances the load between the dual loops when using dual ported devices on the loops. Dynamic load sharing is accomplished by bypassing a given subset of devices off each loop to reduce round trip delay; monitoring traffic on the loops; and controlling which devices are attached to which loop in order to balance the load across the loops. Dynamic system configuration features provide an optimized system configuration on a discretely continuous basis, including implementing dynamic loop sizing, dynamic load sharing, and managing the interconnection of multiple loops and controllers.

Claims

1. A communication system comprising:

(a) at least a first and a second communication link redundantly interconnecting at least a first host device with a plurality of target devices via routing devices, the communication links being enabled for sustaining communication transmissions; and

,

(b) control apparatus enabled to control the routing devices such that the communication transmissions bypass a first subset of the target devices relative to the first communication link, and bypass a second subset of the target devices relative to the second communication link, wherein each subset includes at least one operational target device, and wherein each subset is bypassed during normal communication system operating conditions for improved system performance and efficiency of communication transmissions.

2. The communication system of claim 1 wherein the at least first and second communication links provide point to point communication in a loop topology.

3. The communication system of claim 2 wherein the point to point communication is a serial communication architecture for transmitting data unidirectionally.

4. The communication system of claim 2 wherein each communication link is a separate fibre channel arbitrated loop.

5. The communication system of claim 2 wherein the bypass of each subset reduces a round trip delay of the communication transmissions relative to the loop topology.

6. The communication system of claim 1 wherein a subset of the plurality of target devices are disk drives.

7. The communication system of claim 1 wherein each routing device is a port bypass circuit (PBC) associated with a respective target device and a respective communication link.

8. The communication system of claim 1 wherein the first and second subsets of target devices are established to provide load sharing among the plurality of target devices and communication links.

9. The communication system of claim 1 wherein the at least first and second communication links in combination provide a redundancy configuration for communication transmissions between the at least first host device and plurality of target devices for failover operations and for dynamic management of communication transmissions relative to the communication links and plurality of target devices.

10. The communication system of claim 1 wherein the first and second subsets of target devices are mutually exclusive.

11. The communication system of claim 1 wherein the control apparatus controls the routing devices such that a given operational target device of the plurality of target devices is not bypassed on a given one of the communication links in the event the given target device is bypassed on the other of the communication links.

12. The communication system of claim 1 further including reconfiguration apparatus for dynamically reconfiguring communication links and subsets of devices.

13. The communication system of claim 12 wherein the reconfiguration apparatus dynamically reconfigures the communication links and subsets of devices based on one or more of the following parameters:

communication system operational efficiency, performance and failover objectives, and system growth or reduction in devices.

14. The communication system of claim 12 wherein the reconfiguration apparatus for dynamically reconfiguring the communication links and subsets of devices comprises a routing network and control intelligence for configuring loops and bypassing devices.

15. The communication system of claim 1 wherein the first and second subsets of target devices are overlapping.

16. The communication system of claim 1 wherein the first and second subsets of target devices are the same.

17. A redundant communication system comprising:

(a) one or more fibre channel arbitrated loops interconnecting one or more controller devices and a plurality of target devices via a respective plurality of routing devices;

(b) communication lines interconnecting the one or more controller devices with the routing devices; and

,

(c) management apparatus in connection with the one or more controller devices for managing the routing devices such that communication transmissions bypass a unique subset of the target devices on each loop via the respective routing devices, wherein each subset includes at least one operational target device, and wherein each subset is bypassed during normal communication system operating conditions for improved system performance and efficiency of communication transmissions.

18. A method for improving performance in a redundant communication system having at least one controller device, a plurality of target devices, a respective plurality of routing devices, and at least two communication links interconnecting the at least one controller device and target devices via the routing devices, the method comprising the steps of:

(a) establishing a communication transmission path for each communication link such that a subset of target devices particular to each link are bypassed via the respective routing devices, each subset including at least one operational target device, and wherein each subset is bypassed during normal communication system operating conditions for improved system performance and efficiency of communication transmissions; and

,

(b) enabling communication transmissions to a selected target device via the respective communication link for which the selected target device is not bypassed.

19. The method of claim 18 wherein the communication links provide point to point communication in a loop topology and wherein the bypassing of each subset reduces a round trip delay of the communication transmissions relative to the loop topology.

20. The method of claim 18 wherein each communication link is a separate fibre channel arbitrated loop.

21. The method of claim 18 further including dynamically altering the communication transmission path for one or more of the communication links such that a different subset or subsets of target devices are bypassed.

22. The method of claim 18 further including dynamically altering the communication transmission path for (a) one or more existing communication links, or for (b) one or more existing communication links in connection with (i) the addition of one or more new communication links or (ii) the removal of one or more communication links, based on one or more of the following parameters:

communication system operational efficiency, performance and failover objectives, and system growth or reduction in devices.

23. A communication system comprising:

(a) at least one host device;

(b) a plurality of target devices;

(c) a routing network for interconnecting the at least one host device with any or all of the plurality of target devices, the routing network enabled to sustain communication transmissions; and

,

(d) control apparatus for controlling the routing network for interconnecting the at least one host device with any or all of the plurality of target devices such that fibre channel loops are dynamically formed and such that for at least one of the loops formed over which communication transmissions occur, a subset of target devices, including at least one operational target device, is bypassed to reduce loop transmission delay on that loop as communication transmissions occur over that loop during normal communication system operating conditions.

24. The system of claim 23 wherein the control apparatus is the at least one host device.

25. The system of claim 23 wherein the control apparatus is firmware communicating with the at least one host device.

26. The communication system of claim 23 wherein the loops are dynamically formed based on one or more of the following parameters:

system resources, system work load, system operational efficiency, performance and failover objectives, and system growth or reduction in devices.

27. A computer-readable medium having computer-executable instructions for enabling operation in a redundant communication system having at least one controller device, a plurality of target devices, a respective plurality of routing devices, and at least two communication links interconnecting the at least one controller device and target devices via the routing devices, the computer-executable instructions for performing steps including:

(a) establishing a communication transmission path for each communication link such that a subset of target devices particular to each link are bypassed via the respective routing devices, each subset including at least one operational target device, and wherein each subset is bypassed during normal communication system operating conditions for improved system performance and efficiency of communication transmissions; and

,

(b) enabling communication transmissions to a selected target device via the respective communication link for which the selected target device is not bypassed.