Cuju
Cuju is an open-source software project that delivers virtualization-based fault tolerance using active-passive redundancy. It protects legacy application systems from hardware failures and untrusted hypervisor issues by synchronizing virtual machine states between primary and backup nodes through epoch-based mechanisms. The tool employs advanced performance optimizations including non-stop pipelined continuous migration, dirty tracking for guest virtual memory and device status, and the elimination of data transfer overhead between QEMU and KVM. These features significantly reduce processor usage and synchronization bandwidth while substantially improving virtual machine network throughput and latency. Cuju is designed for deployment across multi-node environments supporting Ubuntu 16.04 and 18.04, requiring Intel virtualization technology and a specific network topology that often includes an NFS node for shared storage and direct high-speed connections between primary and backup servers. This solution ensu