Hardware Reference
In-Depth Information
FIGURE 27.1: Screenshot showing excerpts from the
darshan-job-summary
utility included with Darshan. This example summarizes the I/O behavior of
a 786,432-process turbulence simulation that wrote over 3 TB of data.
the community. The ALCF I/O Data Repository [3] is a notable example. It
provides public access to nearly 200,000 log files collected on the Intrepid Blue
Gene/P system at the ALCF.
27.2 Success Stories
Darshan can fundamentally change the approach to I/O performance en-
gineering on systems where it is deployed. When an I/O performance problem
is observed, scientists and I/O experts can immediately refer to the Darshan
report for initial diagnosis. This often eliminates the need for additional pro-
filing runs (costly in CPU time) or manual source code inspection (costly in
manpower).
Historic collections of Darshan characterization data can also be used to
study trends in system usage as well, as illustrated in this section with example
