A stock market, equity market or share market is the aggregation of buyers and sellers (a loose network of economic transactions, not a physical facility or discrete entity) of stocks (also called shares), which represent ownership claims on businesses; these may include securities listed on a public stock exchange as well as those only traded ...
Redundancy is a system design in which a component is duplicated so if it fails there will be a backup. Redundancy has a negative connotation when the duplication is unnecessary or is simply the result of poor planning.
RAID is short for redundant array of independent disks. Originally, the term RAID was defined as redundant array of inexpensive disks, but now it usually refers to a redundant array of independent disks. RAID storage uses multiple disks in order to provide fault tolerance, to improve overall performance, and to increase storage capacity in a system.