Every modern hard drive has an option to monitor its current status and health via SMART attributes. SMART stands for Self-Monitoring, Analysis, and Reporting Technology. The SMART test can be performed on your HDD to detect any potential problems with the hardware itself. Tests such as these are run using SmartCTL. According to the Linux man page, SmartCTL is a command-line utility designed to perform SMART tasks. Examples of these tasks would be printing error logs or enabling and disabling automatic SMART testing.
RAID (or a Redundant Array of Inexpensive Disks) is a way of storing logical data across a medium which is composed of multiple physical hard disk drives blended into one or more logical units or volumes that is used for data redundancy, performance improvement, and reliability.
High availability is the description of a system designed to be fault-tolerant, highly dependable, operates continuously without intervention, or having a single point of failure. These systems are highly sought after to increase the availability and uptime required to keep an infrastructure running without issue. The following characteristics define a High Availability system.