Abstract: A method and apparatus of performing fault tolerance in a fault tolerant computer system comprising: a primary node having a primary node processor; a secondary node having a secondary node processor, each node further comprising a respective memory; a respective checkpoint shim; each of the primary and secondary node further comprising: a respective non-virtual operating system (OS), the non-virtual OS comprising a respective; network driver; storage driver; and checkpoint engine; the method comprising the steps of: acting upon a request from a client by the respective OS of the primary and the secondary node, comparing the result obtained by the OS of the primary node and the secondary node by the network driver of the primary node for similarity, and if the comparison of indicates similarity less than a predetermined amount, the primary node network driver informs the primary node checkpoint engine to begin a checkpoint process.

Abstract: A method and system of checkpointing in a computing system having a primary node and a secondary node is disclosed. In one embodiment the method includes the steps of determining by the primary node to initiate a checkpoint process; sending a notification to the secondary node, by the primary node, of an impending checkpoint process; blocking, by the primary node, I/O requests from the Operating System (OS) that arrive at the primary node after the determination to initiate the checkpoint process; completing, by the primary node, active I/O requests for data received from the OS prior to the determination to initiate the checkpoint process, by accessing the primary node data storage; and upon receiving, by the primary node, a notice of checkpoint readiness from the secondary node, initiating a checkpoint process to move state and data from the primary node to the secondary node.

Abstract: A method and apparatus of performing fault tolerance in a fault tolerant computer system comprising: a primary node having a primary node processor; a secondary node having a secondary node processor, each node further comprising a respective memory; a respective checkpoint shim; each of the primary and secondary node further comprising: a respective non-virtual operating system (OS), the non-virtual OS comprising a respective; network driver; storage driver; and checkpoint engine; the method comprising the steps of: acting upon a request from a client by the respective OS of the primary and the secondary node, comparing the result obtained by the OS of the primary node and the secondary node by the network driver of the primary node for similarity, and if the comparison of indicates similarity less than a predetermined amount, the primary node network driver informs the primary node checkpoint engine to begin a checkpoint process.

Abstract: A method and system of checkpointing in a computing system having a primary node and a secondary node is disclosed. In one embodiment the method includes the steps of determining by the primary node to initiate a checkpoint process; sending a notification to the secondary node, by the primary node, of an impending checkpoint process; blocking, by the primary node, I/O requests from the Operating System (OS) that arrive at the primary node after the determination to initiate the checkpoint process; completing, by the primary node, active I/O requests for data received from the OS prior to the determination to initiate the checkpoint process, by accessing the primary node data storage; and upon receiving, by the primary node, a notice of checkpoint readiness from the secondary node, initiating a checkpoint process to move state and data from the primary node to the secondary node.

Abstract: A highly available computer system has a primary compute node and a secondary compute node, both of which operate to support at least one similar process using the same instructions and the same information at substantially the same time, and in the event that the secondary compute node generates a read request that is not able to be serviced by cache memory local to it, then the secondary compute node redirects the read request to the primary compute node for servicing.

Abstract: A highly available computer system has a primary compute node and a secondary compute node, both of which operate to support at least one similar process using the same instructions and the same information at substantially the same time, and in the event that the secondary compute node generates a read request that is not able to be serviced by cache memory local to it, then the secondary compute node redirects the read request to the primary compute node for servicing.

Abstract: A fault tolerant computer system having two virtual machines (VMs), each running on a separate host device, is connected over a network to one or more I/O devices. The system operates to monitor the health of one or more operational characteristics associated with each VM, and in the event that the health of both virtual machines dictates that one or the other of the VMs should be downgraded, but the system is not able to determine which VM should be downgraded and there is an imbalance in a monitored system operational characteristic, the system can defer downgrading one VM for a selected period of time during which the operational characteristic that is in imbalance is monitored. If the imbalance is resolved, the downgrade is cancelled, if an operational fault is confirmed prior to the expiration of the deferral period or if the deferral period expires, then one host is downgraded.

Abstract: A method of allowing egress network frames to bypass the buffer requirement of a checkpoint system. In one embodiment, the method includes the steps of examining a frame, or its attributes, to determine if it is a “candidate frame” and if the frame is a candidate frame, allowing it to be released to the external network without an intervening checkpoint. In another embodiment, the candidate frame is one of a group comprising: any frame targeting a designated network interface; any frame of a designated protocol type; any frame sourced or destined from/to a designated address. In still another embodiment, the method includes the designation of scheduling follow-up checkpoints according to frame disposition to limit or reduce the effects of a fail-over (roll-back) disturbance.

Abstract: A method of allowing egress network frames to bypass the buffer requirement of a checkpoint system. In one embodiment, the method includes the steps of examining a frame, or its attributes, to determine if it is a “candidate frame” and if the frame is a candidate frame, allowing it to be released to the external network without an intervening checkpoint. In another embodiment, the candidate frame is one of a group comprising: any frame targeting a designated network interface; any frame of a designated protocol type; any frame sourced or destined from/to a designated address. In still another embodiment, the method includes the designation of scheduling follow-up checkpoints according to frame disposition to limit or reduce the effects of a fail-over (roll-back) disturbance.

Abstract: A fault tolerant computer system having two virtual machines (VMs), each running on a separate host device, is connected over a network to one or more I/O devices. The system operates to monitor the health of one or more operational characteristics associated with each VM, and in the event that the health of both virtual machines dictates that one or the other of the VMs should be downgraded, but the system is not able to determine which VM should be downgraded and there is an imbalance in a monitored system operational characteristic, the system can defer downgrading one VM for a selected period of time during which the operational characteristic that is in imbalance is monitored. If the imbalance is resolved, the downgrade is cancelled, if an operational fault is confirmed prior to the expiration of the deferral period or if the deferral period expires, then one host is downgraded.

Abstract: A fault tolerant computer system is connected over a network with one or more I/O devices. The fault-tolerant computer system has two host devices each of which support a virtual machine (VM) that operates on the same set of instructions (FT application) at substantially the same time, and each VM is allocated space on different virtual containers. In the event that the operational state of one VM is downgraded, due to the unexpected failure of a virtual container associated with it, a mirroring operation is initiated that does not copy empty blocks of information from a source virtual container to a virtual container associated with the downgraded VM if corresponding blocks on the source and the target virtual containers have do not contain any information.