Once the information on the machine has been backed up safely. You can pull out the drive tray for the defective drive. On most units, there will be retaining screws for the drives. Where other manufacturers use plastic retaining clips with pins on them to attach the drive to the tray. Simply remove the screws or retaining clips, swap the drive, replace the screws or clips and re-insert the drive into the machine. Within a matter of minutes, the machine will detect the new drive and begin repairing its RAID settings and initializing the drive for operation in the system.