Load Trace Archive
This page provides pointers to the load traces discussed in these papers:
The first paper (and an earlier description of the work given at LCR
'98) presents a detailed statistical study of these load traces. The
second paper studies the performance of different linear models for
host load prediction. The study is based on data-mining a large-scale
trial of applying different randomly selected prediction models to
randomly selected portions of these load traces. The third paper
describes a system (available below) for playing back load traces to
create realistic workloads. The traces are also used in other parts
of my thesis work on prediction-based
best-effort real-time systems for distributed interactive
applications. Also available is my full list of papers, to which some of the above refer.
Because of the large total size of these files (>800 MB), the machine
that serves them may change from time to time, thus it is advisable to
bookmark this page, instead of the URLs where the actual files
currently reside. If you have difficulty accessing the traces or if
you are interested in accessing the raw data of the prediction study,
please contact firstname.lastname@example.org.
Load trace playback
You can now download a tool to play
these load traces on a machine of your choice.
File format and conversion
The traces are provided in their raw from, and a slightly processed
form which is much easier to download and use. Some selected traces
are also available in compressed ascii.
The format of the raw traces is a sequence of pairs of binary IEEE
doubles stored in Dec Alpha byte order. The first number is a
timestamp, and the second number is the 5 second load average sampled
at that point.
The "combine_host.pl" program will combine
the date of a group of host files in the correct time order.
The "bo_to_text.c" program will convert to
whitespace delimited ascii. If the output looks like garbage, supply
the "-pervert" option to swap byte orders.
The trace filenames have a standard form which encodes the name of
the machine (`hostname`), and the time (`date`) the trace was
started, all sanitized for compatibility with both Unix and NT. For example,
is a trace that was started on August 21, 1997 22:01:59 eastern
daylight time on the machine axp0.psc.edu. All of the traces are
3600 samples long (one hour), except for the first group of PSC
traces, which are 86400 samples long (one day). Trace runs were done
consecutively, so that trace files from a single machine can be
generally be concatenated in time order. Samples are taken at one
In the processed form the traces from a specific host are concatenated
in appropriate time order as described above and converted into
network byte order. Note that while individual raw traces are
contiguous, processed traces may have gaps at times where no raw trace
data was available. If in doubt, use the raw traces or use the
timestamp fields in the processed traces. The processed August 1997
traces from the PSC also have a measurement error corrected. Due to
an off-by-one error in the trace gathering tool, every hundredth
measurement was corrupted. In the processed traces, this measurement
is replaced with an interpolation from the surrounding measurements.
Traces were collected for two time periods, late August 1997 and
February to March 1998 on roughly the same group of machines. There
are two groups of machines. The first is the Alpha cluster at the Pittsburgh Supercomputing Center (PSC).
Of this group, the machines axpfea, axpfeb, and axp0-3 are interactive
machines, while the remainder (axp4-10) are batch machines. The
second group of machines (CMU) are compute servers (mojave, sahara), a
testbed (manchester1-8), and desktop workstations (remainder) in the
CMCL here at CMU.
All of the machines run Digital Unix. Because Digital Unix does not
change the five second load average value more frequently than
approximately every two seconds, we sampled periodically at a rate of
1 Hz. This captures all of the dynamics the operating system makes
available to us.
Some interesting traces in compressed ascii format
The following traces are in a two column whitespace-delimited ascii
format. The first column is the (floating point) time stamp in
seconds and the second column is the measured load value (floating point).
The traces have been gzipped to save space.
All traces in binary format
Here are all of the individual traces in binary format.
A. Dinda for more information.