If available, Cockpit uses the Performance Co-Pilot framework to gather metrics data about the system. This data is used to display graphs. Cockpit can use the PCP logging feature to display archived data about the system from a different point in time. If PCP is not available, then Cockpit gathers the metrics data itself, but archival features are not available.

Whether or not metrics are archived depends on whether the pmlogger.service and pmcd.service systemd units are running or not. The "Store Performance Data" button in Cockpit will enable and start these services.

To see similar metrics data from the command line, you can use tools like pmstat or pminfo:

$ pmstat
@ Sat Sep 26 15:30:10 2015
 loadavg                      memory      swap        io    system         cpu
   1 min   swpd   free   buff  cache   pi   po   bi   bo   in   cs  us  sy  id
    4.19      0 20710m 605148  6450m    0    0    0 2548 5688  14K  19   3  76
...