Orthros: A High-Reliability Operating System with Transmigration of Processes

We propose a method to solve problems that accompany recovering from operating system (OS) failures. First, to reduce recovery time, we make two OSes run simultaneously and configure them as an active-backup structure in one computer. This structure can provide a fast recovery from failures by a failover. Recovery time when using the proposed method is about 0.4 seconds at a minimum and up to about 10 seconds even if 2 GB memory is restored. Next, for smooth continuation of services after recovery, the proposed method preserves processes, their network connections, and file caches, and does not have runtime overhead to obtain a process execution status from the running active OS before a crash. In addition, the resources consumed to build the active-backup structure are only one CPU core and a small amount of memory. The hardware required to implement the proposed method is a multi-core processor and one disk for each OS, consequently, introduction of the proposed method incurs low cost. In the evaluation, we confirmed that the downtime was up to about 1.5 seconds when the active OS of the proposed system crashed while running a text editor, an NFS server, and a database server.