An electronic computing system preserves a pre-error state of a processing unit by receiving a first stream of inputs; buffering the first stream of inputs to generate a buffered stream of inputs identical to the first stream of inputs; conveying the first stream to a primary instance of a first program; conveying the buffered stream to a secondary instance of the first program; executing the primary instance on the first stream in real time; executing the secondary instance on the buffered stream with a predefined time delay with respect to execution of the primary instance on the first stream; detecting an error state resulting from execution of the primary instance; and in response to detecting the error state, pausing the secondary instance and preserving a current state of the secondary instance, wherein the current state of the secondary instance corresponds to a pre-error state of the primary instance.

A system, method, and computer readable medium for hybrid kernel-mode and user-mode checkpointing of multi-process applications. The computer readable medium includes computer-executable instructions for execution by a processing system. A multi-process application runs on primary hosts and is checkpointed by a checkpointer comprised of a kernel-mode checkpointer module and one or more user-space interceptors providing barrier synchronization, checkpointing thread, resource flushing, and an application virtualization space. Checkpoints may be written to storage and the application restored from said stored checkpoint at a later time. Checkpointing is transparent to the application and requires no modification to the application, operating system, networking stack or libraries. In an alternate embodiment the kernel-mode checkpointer is built into the kernel.

As a function equivalent to a first check point restart (CPR) section (CPR function) of a mainframe system, a second CPR section is implemented in an open system. When the mainframe system executes each of job steps that form a job to be migrated from the mainframe system to the open system, the first CPR section outputs a job journal, and when the open system executes the job step migrated from the mainframe system, the second CPR section outputs a job journal, followed by comparison between the outputted job journals.

Examples of the present disclosure describe implementing bitmap-based data replication when a primary form of data replication between a source device and a target device cannot be used. According to one example, a temporal identifier may be received from the target device. If the source device determines that the primary replication method is unable to be used to replicate data associated with the temporal identifier, a secondary replication method may be initiated. The secondary replication method may utilize a recovery bitmap identifying data blocks that have changed on the source device since a previous event.

A system includes a multi-process application that runs on primary hosts and is checkpointed by a checkpointer comprised of a kernel-mode checkpointer module and one or more user-space interceptors providing at least one of barrier synchronization, checkpointing thread, resource flushing, and an application virtualization space. Checkpoints may be written to storage and the application restored from said stored checkpoint at a later time. Checkpointing may be incremental using Page Table Entry (PTE) pages and Virtual Memory Areas (VMA) information. Checkpointing is transparent to the application and requires no modification to the application, operating system, networking stack or libraries. In an alternate embodiment the kernel-mode checkpointer is built into the kernel.

A system and method thereof for performing loss-less migration of an application group. In an exemplary embodiment, the system may include a high-availability services module structured for execution in conjunction with an operating system, and one or more computer nodes of a distributed system upon which at least one independent application can be executed upon. The high-availability services module may be structured to be executable on the one or more computer nodes for loss-less migration of the one or more independent applications, and is operable to perform checkpointing of all state in a transport connection.

A system is provided for creating selective snapshots of a database that is stored as one or more segments, wherein a segment comprises one or more memory pages. The system includes a memory storage comprising instructions and one or more processors in communication with the memory. The one or more processors execute the instructions to determine whether a snapshot process is configured to access a selected segment of the one or more segments, assign a positive mapping status to an accessed segment for which the determining unit has determined that it is accessed by the snapshot process and to assign a negative mapping status to a non-accessed segment, and create a snapshot comprises a step of forking the snapshot process with an address space that comprises a subset of the one or more segments.

A checkpointing method in a network device fault tolerant system using virtual machines. In one embodiment, the network device has an input port, an output port, an active virtual machine and a standby virtual machine, a network application on the active virtual machine which manipulates data present on the input port and transmits the manipulated data from the output port; a checkpoint engine on the active virtual machine; and an interface agent, on the active virtual machine, having callable functions to move data from the input port to the output port. The method includes the steps of determining, by the checkpoint engine, that a checkpoint is required; requesting by the checkpoint engine that the interface agent quiescent itself; returning, by the interface agent to the network application, an indicator that no packets are available regardless of whether or not packets are arriving at the input port.

Examples provide a fault tolerant virtual machine (VM) using pooled memory. When fault tolerance is enabled for a VM, a primary VM is created on a first host in a server cluster. A secondary VM is created on a second host in the server cluster. Memory for the VMs is maintained on a shared partition in pooled memory. The pooled memory is accessible to all hosts in the cluster. The primary VM has read and write access to the VM memory in the pooled memory. The secondary VM has read-only access to the VM memory. If the second host fails, a new secondary VM is created on another host in the cluster. If the first host fails, the secondary VM becomes the new primary VM and a new secondary VM is created on another host in the cluster.

A method for resumeable snapshot deletion is provided. A method for deletion of nodes maintained in an ordered data structure for a first snapshot includes processing the nodes maintained in the ordered data structure according to a defined order, setting a node path cursor with a pointer to a node and an indication of the deletion of the node; storing the node path cursor in a persistent storage; and during processing of the nodes: detecting a failure; after the failure, checking the pointer of the node path cursor; and resuming processing of the nodes starting from the first node indicated by the pointer.