Input/output optimization and disk architectures: A survey

The file system, and the components of the computer system associated with it (disks, drums, channels, mass storage, tapes and tape drives, controllers, I/O drivers, etc.) comprise a very substantial fraction of most computer systems; substantial in several aspects including amount of operating system code, expense for components, physical size and effect on performance. In this paper we survey the state of the art file and I/O system design and optimization as it applies to large data processing installations. In a companion paper, some research results applicable to both current and future system designs are summarized.Among the topics we discuss is the optimization of current file systems, where some material is provided regarding block size choice, data set placement, disk arm scheduling, rotational scheduling, compaction, fragmentation, I/O multipathing and file data structures. A set of references to the literature, especially to analytic I/O system models, is presented. The general tuning of file and I/O systems is also considered. Current and forthcoming disk architectures are the second topic. The count key data architecture of current disks (e.g. IBM 3350, 3380) and the fixed block architecture of new products (IBM 3310, 3370) are compared. The use of semiconductor drum replacements is considered and some commercially available systems are briefly described.