You can zoom on the graphs by selecting an area of one of them, then unzoom with a double-click.

SAR Charts is a web interface for displaying data, provided by SAR (System Activity Report, from the sysstat package) on Linux and Unix servers, with graphs.

SAR file importation

 
• Sample files to download for testing:
How to export a SAR file
The location of the files varies according to the distribution: /var/log/sa, /var/log/sysstat, /var/adm/sa...
For a single file:
# sar -A -f <path>/saXX > /tmp/saXX_$(uname -n).txt
For multiple files:
# cd <path> && find . -name 'sa??' -type f -exec sh -c 'for f; do sar -A -f ${f} > /tmp/${f}_$(uname -n).txt; done' _ {} +