Abstract: High availability (HA) protection is provided for an executing virtual machine. At a checkpoint in the HA process, the active server suspends the virtual machine; and the active server copies dirty memory pages to a buffer. During the suspension of the virtual machine on the active host server, dirty memory pages are copied to a ring buffer. A copy process copies the dirty pages to a first location in the buffer. At a predetermined benchmark or threshold, a transmission process can begin. The transmission process can read data out of the buffer at a second location to send to the standby host. Both the copy and transmission processes can operate asynchronously on the ring buffer. The ring buffer cannot overflow because the transmission process continues to empty the ring buffer as the copy process continues. This arrangement allows for using smaller buffers and prevents buffer overflows, and thereby, it reduces the VM suspension time and improves the system efficiency.

Abstract: High availability (HA) protection is provided for an executing virtual machine. At a checkpoint in the HA process, the active server suspends the virtual machine; and the active server copies dirty memory pages to a buffer. During the suspension of the virtual machine on the active host server, dirty memory pages are copied to a ring buffer. A copy process copies the dirty pages to a first location in the buffer. At a predetermined benchmark or threshold, a transmission process can begin. The transmission process can read data out of the buffer at a second location to send to the standby host. Both the copy and transmission processes can operate substantially simultaneously on the ring buffer. As such, the ring buffer cannot overflow because the transmission process continues to empty the ring buffer as the copy process continues. This arrangement allows for smaller buffers and prevents buffer overflows.

Abstract: High availability (HA) protection is provided for an executing virtual machine. A standby server provides a disk buffer that stores disk writes associated with a virtual machine executing on an active server. At a checkpoint in the HA process, the active server suspends the virtual machine; the standby server creates a checkpoint barrier at the last disk write received in the disk buffer; and the active server copies dirty memory pages to a buffer. After the completion of these steps, the active server resumes execution of the virtual machine; the buffered dirty memory pages are sent to and stored by the standby server. Then, the standby server flushes the disk writes up to the checkpoint barrier into disk storage and writes newly received disk writes into the disk buffer after the checkpoint barrier.

Abstract: A system for enabling communication between a first domain and a second domain is disclosed. At least the first domain is protected by a firewall. A first data-processing system is provided in the first domain and a second data-processing system provided in second domain. The second domain hosts an application that the first domain desires to access. To enable the communication between the two domains a tunnel is established through the firewall. The tunnel runs from the first data-processing system to the second data-processing system. The second data-processing system provides a web-proxy interface to interface to the application and also acts as a tunnel gateway.

Abstract: A system for providing two-way Web services is disclosed that enables the client and server to be in different enterprise domains—behind firewalls—with few or no changes to the firewalls. In accordance with the illustrative embodiment, a “tunnel hub” is deployed in the public domain and “tunnel gateways” are deployed behind the firewalls where the clients request two-way services and the servers provide two-way services. Each tunnel gateway initiates a secure tunnel out through the firewall to the target hub. Thereafter, a request for service enters the tunnel gateway, travels to the tunnel hub and to the appropriate tunnel gateway where the server is that provides the service. When the server provides the service, it enters the tunnel gateway, travels to the tunnel hub and to the appropriate tunnel gateway where the client is that requested the service.