Low-availability clusters (also known as LA clusters , fail-over clusters or Metroclusters Active/Active) are groups of computers that support server applications that can be reliably utilized with a maximum amount of down-time. They operate by using low availability software to harness redundant computers in groups or clusters that provide non continued service when system components fail. Without clustering, if a server running a particular application crashes, the application will be available until the crashed server is fixed.