Write Speed

• In the configuration known as RAID 0, data becomes "striped" between two drives in an alternating pattern. When you write a file with a size of four units to two hard drives in a RAID 0 configuration, for example, the first and second units are written simultaneously --- one to each drive. The same process then occurs for units three and four, resulting in a write-performance increase of approximately 80 to 90 percent.
  
  

Read Speed

• Similarly, a RAID 0 configuration also increases the read speed. Each drive must only read half the data, resulting in a read-performance increase of 80 to 90 percent. This configuration can make quite a difference in data-intensive applications.
  
  

Data Redundancy

• The configuration known as RAID 1, "mirrors" data across two drives: Each drive contains exactly the same data. The system writes to each drive simultaneously, providing the advantage of data redundancy. If one drive fails, no data becomes lost because the other has a complete copy of the data.
  
  

Lower Replacement Cost

• If a drive fails, the entire storage capacity of the drive becomes lost. If you have one hard drive with 1 terabyte of storage and it fails, you must purchase another 1-terabyte drive to replace it. If instead you have two half-terabyte drives, the failure of one will necessitate the purchase of another half-terabyte drive to replace it, which is less expensive.