Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
2001-10-23
2004-03-30
Beausoliel, Robert (Department: 2184)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C714S005110
Reexamination Certificate
active
06715098
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns “port spoofing,” which allows a computer to “fail over” to its secondary fibrechannel connection if its primary fibrechannel connection should fail.
Fibrechannel is a network and channel communication technology that supports high-speed transmission of data between two points and is capable of supporting many different protocols such as SCSI (Small Computer Systems Interface) and IP (Internet Protocol). Computers, storage devices and other devices must contain a fibrechannel controller or host adapter in order to communicate via fibrechannel. Unlike standard SCSI cables, which can not extend more than 25 meters, fibrechannel cables can extend up to 10 km. The extreme cable lengths allow devices to be placed far apart from each other, making it ideal for use in disaster recovery planning. Many companies use the technology to connect their mass storage and backup devices to their servers and workstations.
In addition to being able to protect data through disaster recovery plans and backup, another requirement for a computer data communications network is that the storage devices must always be available for data storage and retrieval. This requirement is called “High Availability.” High Availability is a computer system configuration implemented with hardware and software such that, if a device fails, another device or system that can duplicate the functionality of the failed device will come on-line to take its place automatically and transparently. Users will not be aware that a failure and switch-over had taken place if the system is implemented properly. Many companies cannot afford to have downtime on their computer systems for any length of time. High availability is used to ensure that their computer systems remain running continuously in the event of any device failure. Servers, storage devices, network switches and network connections are redundant and cross-connected to achieve High Availability.
FIG. 1
shows a typical prior art fibrechannel High Availability configuration.
In the configuration of
FIG. 1
, High Availability is achieved by first creating mirrored storage devices
145
and
150
and then establishing multiple paths to the storage devices which are represented by the fibrechannel connections
105
,
110
,
125
,
130
,
135
, and
140
. This configuration allows the server
100
to continuously be able to store and retrieve its data, even if multiple failures have occurred, as long as one of its redundant hardware components or fibrechannel connections does not fail. For example, if paths
110
and
125
fail, the data traffic will be routed through paths
105
and
140
to access storage device
150
. Special software must be running on the server to detect the failures and route the data through the working paths. The software is costly and requires valuable memory and CPU processing time from the server to manage the fail-over process.
SUMMARY OF THE INVENTION
The present invention is a system and method of achieving High Availability on fibrechannel data paths between an appliance's fibrechannel switch and its storage device by employing a technique called “port spoofing.” This system and method do not require any proprietary software to be executing on the file/application appliance other than the software normally required on an appliance, which includes the operating system software, the applications, and the vendor-supplied driver to manage its fibrechannel host adapter(s).
The invention includes a system for appliance back-up, in which a primary appliance is coupled to a network, whereby the primary appliance receives requests or commands and sends a status message over the network to a standby appliance, which indicates that the primary appliance is operational. If the standby appliance does not receive the status message or the status message is invalid, the standby appliance writes a shutdown message to a storage device, which is also coupled to the network. The primary appliance then reads the shutdown message stored in the storage device and disables itself from processing requests or commands. Preferably, when the primary appliance completes these tasks, it disables communication connections and writes a shutdown completion message to the storage device. The standby appliance reads the shutdown completion message from the storage device and initiates a start-up procedure, which includes causing the address of the standby appliance to be identical to the primary appliance address and processing the requests or commands in place of the primary appliance. The primary appliance can include a fibrechannel adapter having associated therewith the primary appliance address, and the standby appliance can have a fibrechannel adapter having associated therewith the standby appliance address. The standby appliance can include a standby application, which is identical to a primary application in the primary appliance, for processing the requests or commands.
The invention also includes a method for appliance back-up, which includes sending a status message from a primary appliance to a standby appliance indicating that the primary appliance is operational. If the standby appliance does not receive the status message or the status message is invalid, a shutdown message is written to a storage device. The primary appliance reads the shutdown message stored in the storage device and is disabled from processing requests or commands. The disabling of the primary appliance can include completing tasks, disabling communication connections, and writing a shutdown completion message to the storage device. The standby appliance reads the shutdown completion message from the storage device and initiates a start-up procedure so that a standby application, included in the standby appliance, can process the requests or commands. A standby appliance address is changed to the primary appliance address and the standby appliance processes the requests or commands.
Another method for appliance back-up is disclosed which includes monitoring a primary appliance for an indication of a failure, the primary appliance having a primary appliance address. If the failure occurs, a message is written to a storage device and, in response, the primary appliance is disabled from processing requests or commands. The failure can be the primary appliance not sending the status message to a standby appliance. The standby appliance has a standby appliance address, which is changed to the primary appliance address so the standby appliance can processes the requests or commands. The standby appliance address and the primary appliance address are world wide port names. The monitoring can include sending a status message to the standby appliance indicating that the primary appliance is operational, or sending a status request message to the primary appliance and receiving an update status message from the primary appliance. The failure message is written if the standby appliance does not receive the status message or if the status message is invalid. Alternatively, the message is written if the standby appliance does not receive the update status message or the update status message is invalid. The disabling can include completing tasks, disabling communication connections, writing a shutdown completion message to the storage device (by the primary appliance), reading the shutdown completion message from the storage device (by the standby appliance), and initiating a start-up procedure. The standby appliance can include a standby application, which is identical to a primary application in the primary appliance, for processing the requests or commands.
One of the primary advantages of the present invention is that additional software is not required to be running on the file/application server. Many system administrators prefer to only install the software that is necessary to run their file/application servers. Many other solutions require special software or drivers to run on the server in order to manage the fail-over proced
Chen Sheng-Wei
McNulty Stephen Anthony
Beausoliel Robert
Bonzo Bryce P.
FalconStor, Inc.
Schildkraut Mark
Scholer LLP Kaye
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