Virtual machine (VM) replication is a well known technique for providing application-agnostic software-implemented hardware fault tolerance "non-stop service". High availability solutions such as Remus and COLO will do consecutive checkpoint. The VM state of Primary VM and Secondary VM is identical right after a VM checkpoint, but becomes different as the VM executes till the next checkpoint. COLO is more of a Fault Tolerance solution, Both primary VM (PVM) and secondary VM (SVM) are run in parallel. They receive the same request from client, and generate response in parallel too. If the response packets from PVM and SVM are identical, they are released immediately. Otherwise, a VM checkpoint (on demand) is conducted. There's an academia paper in SOCC 2013: http://www.socc2013.org/home/program. In this talk, we will present the latest progress from Fujitsu, Intel and Huawei.