There is an old Canadian folk song that says: "... you don't know what you got 'til its gone." This is the value of a file. What will it cost your organization if the file is lost? This is the flip side of the security question: What is the cost if a file is read or manipulated by the wrong person? The costs may be tangible or intangible. For example, if a word processing file containing a memo about the company picnic five years ago is lost, the cost could be zero. If the memo was for this year's picnic, the cost would be the labor cost of re-entering. If the memo was a response to a bid that is due tomorrow, the cost becomes time-sensitive. The momentary cost is the cost of labor, but the real cost is the profits of the contract, if the file cannot be re-entered in time to make the bid closing. Fault tolerance and data recovery is about minimizing the cost of lost data, while attempting to limit the cost of resources needed.
Many tools can be used to minimize the cost of lost data. These tools are UPS, tape backup, disk mirroring, disk duplexing, and striping with parity.