Method for communicating a software-generated pulse waveform between two servers in a network

• US 6,163,853 A
• Filed: 10/01/1997
• Issued: 12/19/2000
• Est. Priority Date: 05/13/1997
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micro Electronics Incorporated
• Inventors: Chrabaszcz, Michael, Findlay, Bruce
• Primary Examiner(s): Hua, Ly V.
• Application Number:
  US08/942,221
• Time in Patent Office: 1,175 Days
• Field of Search: 714/4, 714/47, 714/10, 714/39
• US Class Current: 714/4.4
• CPC Class Codes: G06F 11/0709 in a distributed system consisting of a plurality of standalone computer nodes, e.g. clusters, client-server systems
• CPC Class Codes: G06F 11/0745 in an input/output transactions management context input/output processing in general G06F13/00
• CPC Class Codes: G06F 11/0757 by exceeding a time limit, i.e. time-out, e.g. watchdogs
• CPC Class Codes: G06F 11/0772 Means for error signaling, e.g. using interrupts, exception flags, dedicated error registers
• CPC Class Codes: G06F 11/3006 where the computing system is distributed, e.g. networked systems, clusters, multiprocessor systems multiprogramming arrangements G06F9/46; allocation of resources G06F9/50
• CPC Class Codes: G06F 11/3034 where the computing system component is a storage system, e.g. DASD based or network based digital input from or digital output to record carriers G06F3/06; digital recording or reproducing G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097
• CPC Class Codes: G06F 11/3048 where the topology of the computing system or computing system component explicitly influences the monitoring activity, e.g. serial, hierarchical systems
• CPC Class Codes: G06F 11/3055 Monitoring arrangements for monitoring the status of the computing system or of the computing system component, e.g. monitoring if the computing system is on, off, available, not available error or fault processing without redundancy G06F11/0703; error detection or correction by redundancy in data representation G06F11/08; error detection or correction by redundancy in operation G06F11/14; error detection or correction by redundancy in hardware G06F11/16
• CPC Class Codes: G06F 11/3065 Monitoring arrangements determined by the means or processing involved in reporting the monitored data error or fault reporting or logging G06F11/0766
• CPC Class Codes: H04L 41/06 Management of faults, events, alarms or notifications
• CPC Class Codes: H04L 41/12 Discovery or management of network topologies
• CPC Class Codes: H04L 43/0805 by checking availability
• CPC Class Codes: H04L 43/0817 by checking functioning
• CPC Class Codes: H04L 43/10 Active monitoring, e.g. heartbeat, ping or trace-route
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06

Abstract

A method of monitoring a status condition of a first server with a second server in a server network, and also providing synchronization and messaging between the two servers, the method including: transmitting a software-generated pulse waveform from the first server to a device coupled to the first server, wherein the software-generated pulse waveform is comprises a first command corresponding to a logic level low and a second command corresponding to a logic level high; setting said device to a first state during logic level lows of said pulse waveform and to a second state during logic level highs of said pulse waveform; receiving the software-generated pulse waveform with the second server by determining when said device is in the first state and when it is in the second state; and determining when said device no longer changes from the first state to the second state. In order to provide synchronization and messaging, said pulse waveform is frequency modulated in order to communicate specified commands and/or reference points between the two servers.

Claims

1. A method of monitoring an operational status of a first server with a second server, comprising:

successively transmitting first and second command signals to a device coupled to the first server, wherein the first command signal places the device in a first status condition and the second command signal places the device in a second status condition; and

monitoring a status condition of the device with the second server, coupled to the device, wherein a change in the status condition of the device indicates that the first server is operational.

2. The method of claim 1 wherein the act of successively transmitting first and second command signals to a device comprises successively transmitting a Reserve Unit command and a Release Unit command to a SCSI device, wherein the Reserve Unit command places the SCSI device in a reserved status and the Release Unit command places the device in a released status.

3. The method of claim 2 wherein the act of monitoring the status condition of the device with the second server comprises:

transmitting a series of Test Unit Ready commands to the device at a predetermined sampling rate; and

receiving a response to each of the Test Unit Ready commands from the device, wherein each response indicates either a successful test, corresponding to a released status of the device, or a failed test, corresponding to a reserved status of the device.

4. The method of claim 3 further comprising:

determining a reservation time period corresponding to a period of time that the device is continuously in a reserved status, wherein the reservation time period represents a logic level high of a software-generated pulse waveform;

determining a release time period corresponding to a period of time that the device is continuously in a released status, wherein the release time period represents a logic level low of the software-generated pulse waveform;

determining a first reference point on the pulse waveform corresponding to a reserved status;

determining a second reference point on the pulse waveform corresponding to a released status; and

thereafter, transmitting the Test Unit Ready command to the device only at times corresponding to the first and second reference points.

5. The method of claim 4 wherein:

the act of determining the first reference point comprises determining a location corresponding to a rising edge on the pulse waveform and determining a location corresponding to a falling edge on the pulse waveform, wherein the first reference point is chosen off-phase from both the rising and falling edges; and

the act of determining the second reference point comprises selecting a point on the pulse waveform which is approximately (N times

     360)+180 degrees out of phase from the first reference point, where N is an integer greater than or equal to zero.

6. The method of claim 4 further comprising:

determining if a first response signal received in response to the Test Unit Ready signal transmitted to the device at the first reference point matches an expected response; and

determining if a second response signal received in response to the Test Unit Ready signal transmitted to the device at the second reference point matches an expected response.

7. The method of claim 6 additionally comprising if it is determined that either the first response signal or the second response signal does not match its respective expected response, initiating a recalibration procedure, comprising:

transmitting a second series of Test Unit Ready commands to the device at the predetermined sampling rate;

receiving a response to each of the Test Unit Ready commands of the second series, wherein each response indicates either a successful test, corresponding to a released status of the device, or a failed test, corresponding to a reserved status of the device;

determining if the pulse waveform is still present, wherein if the status of device changes, the pulse waveform is determined to be present and if the status of the waveform does not change, the pulse waveform is determined to be absent and the first server is deemed to have failed; and

if the pulse waveform is determined to be present initiating the following acts;

determining a second reservation time period corresponding to a period of time that the device is continuously in a reserved status, wherein the second reservation time period represents the logic level high of the software-generated pulse waveform;

determining a second release time period corresponding to a period of time that the device is continuously in a released status, wherein the second release time period represents the logic level low of the software-generated pulse waveform;

determining a third reference point on the pulse waveform;

determining a fourth reference point on the pulse waveform; and

thereafter transmitting the Test Unity Ready command only at times corresponding to the third and fourth reference points.

8. A method of monitoring a status condition of a first server with a second server in a server network, comprising:

transmitting a software-generated pulse waveform from the first server to a device coupled to the first server, wherein the software-generated pulse waveform comprises a first command corresponding to a logic level low and a second command corresponding to a logic level high;

setting the device to a first state during logic level lows of the pulse waveform and to a second state during logic level highs of the pulse waveform;

receiving the software-generated pulse waveform with the second server by determining when the device is in the first state and when it is in the second state; and

determining when the device no longer changes from the first state to the second state.

9. The method of claim 8 further comprising determining the shape and frequency of the software-generated pulse waveform.

10. The method of claim 9 wherein the act of determining the shape and frequency of the software-generated pulse waveform, comprises:

sampling the pulse waveform at a sampling frequency which is greater than the frequency of the pulse waveform for at least one cycle of the pulse waveform; and

recording the transition points of the pulse waveform.

11. The method of claim 10 wherein the act of determining when the device no longer changes from the first state to the second state, comprises monitoring the pulse waveform at a reference point which is expected to correspond to a logic level high on the waveform and detecting when the reference point is not at the logic level high.

12. The method of claim 10 wherein the act of sampling the pulse waveform comprises:

repetitively sending a test command to the device at the sampling rate; and

receiving a response to each test command, indicating whether the device is in the first state or the second state, wherein the first state is translated into the logic level low of the pulse waveform and the second state is translated into the logic level high of the pulse waveform.

13. A method of monitoring a status condition of a first server by a second server, comprising:

transmitting SCSI Reserve and Release commands from the first server to a SCSI device, coupled to the first server; and

monitoring a released/reserved status of the SCSI device with the second server.

14. The method of claim 13 wherein a change in the released/reserved status of the SCSI device indicates that the first server is operational and a constant reserved status of the SCSI device indicates that the first server has failed.

15. The method of claim 13 wherein the Reserve and Release commands are successively transmitted to the SCSI device so as to place the SCSI device in successive states of reserved and released, wherein the states of the device serve as a basis for a software-generated pulse waveform which is received by the second server.