Parallel File System Workload Characterization

Most parallel file systems (eg, Intel's CFS, Thinking Machines SFS) have been designed around the assumption that scientific applications running on parallel computers would exhibit behavior similar to that of scientific applications running on uniprocessors and vector supercomputers.

The primary characteristics of file access in those environments are:

To test the validity of that assumption, we traced the workloads of two different parallel file systems, on two different machines, at two different sites, running primarily scientific applications. The tracing involved recording every single access that was made to the parallel file system over a period of weeks.

The two machines we traced were an Intel iPSC/860 at NASA Ames' Numerical Aerodynamic Simulation facility and a Thinking Machines CM-5 at the National Center for Supercomputing Applications . All parallel file access on the iPSC was done through Intel's Concurrent File System. Parallel applications on the CM-5 could use either the data-parallel CMF I/O library or the control parallel CMMD I/O library.

Our observations may be summarized as follows:

We examined the millions of small, noncontiguous requests in greater detail, and found that most of them appeared to be part of regular, higher-level pattern.

The experiments, our observations, and our conclusions are examined in much greater detail in the following papers:

Nils A. Nieuwejaar
Last modified Friday, March 29, 1996