smartd - SMART Disk Monitoring Daemon in linux

The purpose of SMART disk monitoring system is to monitor the reliability of the hard drive and predict drive failures, and to carry out different types of drive self-tests in unix or linux.SMART, or Self-Monitoring, Analysis, and Reporting Technology is a capability that's built into almost all modern IDE and SCSI disk drives that allows the drive controller to monitor it's health. SMART-capable drive can give clues like when a drive is about to fail. Smartd is part of the smartmontools package and runs as a daemon on your system.Smartd Entries are logged to SYSLOG (by default /var/log/messages.)
you can start smartd by giving the command:

/etc/rc.d/init.d/smartd start

and stop it by using the command:

/etc/rc.d/init.d/smartd stop

If you want smartd to start running whenever your machine is booted, it can be done by the following command:

/sbin/chkconfig --add smartd

and disabled using the command:

/sbin/chkconfig --del smartd
You can also check the status of smartd in system configuration menu. Use system->Administration->serversettings->services.