This report describes a series of experiments to investigate the performance of SCSI disks as seen by the application programmer. The results show a significant performance loss, on the order of 50%, when two or more files are simultaneously read from the same disk. Performance is also reduced when files are stored in an interleaved manner, and when small block sizes are utilized. Keywords: SCSI disk performance, file system performance, parallel file system performance. R'esum'e Ce rapport d'ecrit une s'erie d'exp'eriences pour 'etudier la performance des disques SCSI telles qu'aper¸cues `a l'interface de programmation. Les r'esultats indiquent une r'eduction significante de performance, de l'ordre de 50%, lorsqu'au moins deux fichiers sont simultan 'ement lus de la meme disque. La performance est aussi r'eduite lorsque des fichiers sont stock'es de fa¸con interfoli`ee et lorsque des blocs de petite taille sont utilis'es. Mots-cl'es: performance de disques SCSI, performance de syst...

This report describes three application program interfaces to BPFS, a distributed, modular parallel file system designed for use on clusters of workstations. These interfaces are called API0, CLI, and MPI-IO. API0 is the first of an anticipated series of low-level, experimental client interfaces to BPFS. It is an "unconventional" interface in many respects: it is not particularly "UNIX-like", it is blockoriented rather than byte oriented, it reads and writes system buffers as well as user-defined data areas, and it is asynchronous. It also provides time-regulated "data streaming" operations and userlevel control of both server-side caching and per-file striping onto disks. Although API0 can be used directly from a user application program, it can also be used "under" a more conventional interface, as has been done for the next two interfaces. CLI is a "C Library Interface" implemented on top of API0 that exactly mimics the Standard C I/O library interface, but accesses parallel files s...