Stratus Technologies Bermuda Ltd.

Stratus Technologies, Inc

Srinivasu Chinta

Paul A Leveille

Thomas D Bissett

Stephen J Wark

Leslie R Sibley

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.

Method of selective network buffering in checkpoint systems

A method of delaying checkpointing in a virtual machine system. In one embodiment, the method includes the steps of examining a network frame to determine if it is a deferrable frame and if the frame is a deferrable frame, delaying a checkpoint associated with the frame. In another embodiment, the deferrable frame is one of a group comprising: an IP packet tagged with the 'more fragments' attribute; TCP data segments that lack the PSH flag and carry no flags other than 'ACK'; and TCP segments that contain no data and carry only the &#x2018;ACK&#x2019; flag; and any frame originating from or destined to a designated network address or port number. In still another embodiment, the method includes the step of concatenating the delays due to deferrable frames. In still yet another embodiment, the method further includes setting an upper limit to the amount of delay that can be generated.

Method of delaying checkpoints by inspecting network packets

A method for determining a delay in a dynamic, event driven, checkpoint interval. In one embodiment, the method includes the steps of determining the number of network bits to be transferred; determining the target bit transfer rate; calculating the next cycle delay as the number of bits to be transferred divided by the target bit transfer rate. In another aspect, the invention relates to a method for delaying a checkpoint interval. In one embodiment, the method includes the steps of monitoring the transfer of a prior batch of network data and delaying a subsequent checkpoint until the transfer of a prior batch of network data has reached a certain predetermined level of completion. In another embodiment, the predetermined level of completion is 100%.

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Nashua, NH, United States of America

Srinivasu Chinta