I could not find anywhere an explanation of what HP nonstop is actually doing. The fact you say its like VMWare make me think you mean VMware vLockstep. Documen

I could not find anywhere an explanation of what HP nonstop is actually doing. The fact you say its like VMWare make me think you mean VMware vLockstep. Documentation say : "While both the primary and secondary VMs receive the same inputs, only the primary VM produces output such as disk writes and network transmits." The part I don't understand is how can the primary wait for the secondary to execute the same cpu instruction before producing output? this would be extremely slow even with very good network latency. Also it seem in vsphere6 VMware have rewritten how FT is handled, dropping the old “lock-step” approach in favour of a new “fast check-pointing” type method. If the memory content on the secondary is not exactly the same as what was on the primary before the crash. Then there is some kind of small dataloss. This is the kind of thing I assumed could only be solved by having the primary run a consensus protocol like Raft or Paxos for each network request it receive before producing response to the request.