RAID, or Redundant Array of Independent Disks, combines multiple hard drives together in order to improve efficiency, with varying effects.
There are three main types of RAID - RAID 0, RAID 1 and RAID 5. It is a storage virtualisation that combines multiple hard drivesinto a single logical unit to provide increased capacity reliability and most importantly redundancy. In theory of a single hard drive fails, the redundancy allows the data to be rebuilt by the RAID controller.
RAID 0 turns two (or more) hard disk drives into one single, bigger and faster storage device. But, the chance of data loss is significantly greater. Data is stored across all of the drives, so if you have four drives in your RAID, there's effectively 4x the chance of a data loss incident. RAID 1 is also known as 'disk mirroring', and replicates your data across two or more disks, allowing data to be read incredibly fast. If one fails, the other(s) keep working, which means data loss is less likely. But, you only have the capacity of one drive, which means it can be costly. Plus, your data still isn't 100% safe - there's still a risk of all the disks becoming damaged via a drop or natural disaster. RAID 5 offers the best of both worlds - capacity, speed and protection. All but one of the drives are used for storage, with this extra drive containing the parity information that is needed to rebuild the RAID in the event of a failure.