The sysstat package contains numerous tools for monitoring performance and load states on systems, including iostat, mpstat, and pidstat. In addition to tools intended for ad hoc use, sysstat comes with a collection of utilities that you schedule for periodic use as cron jobs (e.g., sar). The compiled statistics range from I/O transfer rates, CPU and memory utilization, paging and page faults, network statistics, and filesystem utilization through NFS server and client activities.
Of course, you could use top, vmstat, ss, and so on to determine the data, but bear in mind that system events are hardly likely to be restricted to the times at which you are sitting in front of the screen. Admins typically receive requests for more detailed information, like: “What exactly happened on system XY between…