It's also possible to get disk I/O data out of sar, but this is even less likely to be turned on by default due to concerns about collection overhead (specifically disk space used to save the data). The following is the common error you run into:
$ sar -d Requested activities not available in file
sar works by collecting data through cron. On RHEL/CentOS Linux, the configuration file that does so is at /etc/cron.d/sysstat; it defaults to collection every 10 minutes, but you can make that more or less often by tuning it. This calls the sa1 shell script, which then runs the sadc (system activity data collector). sadc is the utility that you pass a flag to in order to have it collect disk activity. ...
