Kernel-level single system image for petascale computing

Scientific computing users typically prefer UNIX or UNIX-like operating systems as their runtime for managing software and hardware resources. These UNIX-like systems were originally designed for a single processor as well as for a broad range of programming and usage models. Although UNIX-like systems have successfully been modified to work in SMP or NUMA configuration, their internal structures remain relatively the same over the years. As we move toward the era of petascale computing, these UNIX-like systems are no longer suitable. For instance, the relative cost of supporting generic usages and system services will increase by a magnitude and thus affect the overall system performance; there are insufficient system services to globally manage parallelism, processes, and resources; users may not see the petascale system as a single powerful machine but rather as a set of multiple independent servers. A single system image (SSI) operating system is essential for efficiently manage parallelism, resources and processes as well as providing parallel processing transparency for a system possibly equipped with hundred thousand of processors. However, the success of a petascale SSI operating system goes beyond technical challenges. In particular, it must look very much like the normal UNIX, run unmodified software, scale incrementally, and equip with built-in high availability supports. This position paper focuses on these issues and discusses the development of a petascale SSI, based on an existing kernel-level SSI system, OpenSSI.