VPC: Scalable, Low Downtime Checkpointing for Virtual Clusters

A virtual cluster (VC) consists of multiple virtual machines (VMs) running on different physical hosts, inter-connected by a virtual network. A fault-tolerant protocol and mechanism are essential to the VC´s availability and usability. We present Virtual Predict Check pointing (or VPC), a lightweight, globally consistent check pointing mechanism, which checkpoints the VC for immediate restoration after VM failures. By predicting the checkpoint-caused page faults during each check pointing interval, VPC further reduces the solo VM downtime than traditional incremental check pointing approaches. Besides, VPC uses a globally consistent check-pointing algorithm, which preserves the global consistency of the VMs´ execution and communication states, and only saves the updated memory pages during each check pointing interval to reduce the entire VC downtime. Our implementation reveals that, compared with past VC check pointing/migration solutions including VNsnap, VPC reduces the solo VM downtime by as much as 45%, under the NPB benchmark, and reduces the entire VC downtime by as much as 50%, under the NPB distributed program. Additionally, VPC incurs a memory overhead of no more than 9%. In all cases, VPC´s performance overhead is less than 16%.