Multi-site Synchronous VM Replication for Persistent Systems with Asymmetric Read/Write Latencies

Novel non-volatile memory is considered as a future replacement for conventional main memory. While besides persistence non-volatile memory technologies promise higher storage density and lower power demand, they also possess an asymmetry between fast read and slow write access times. The latter can be in the order of 2x to even 20x. While persistent main memory per se asks for novel system software support, the asymmetry between read and write access times needs to be addressed for building efficient solutions. This paper addresses virtual machine replication for high availability when non-volatile memory is put in use. So far asynchronous VM replication that stops a virtual machine, performs a local copy of dirty pages, resumes the virtual machine, before the data is transferred to a back-up site, is the state of the art. In contrast, we propose a multi-site zero-copy synchronous VM replication, which utilizes Remote Direct Memory Access and is tolerant to different read/write latencies. We demonstrate that for future hardware settings synchronous VM replication provides a performance increase of up to 27% compared to current best practices.