To be accurate, the phrase "data recovery" refers to the process where data is saved from storage media that has either been corrupted, damaged, failed, or made inaccessible for some reason. When data can not be accessed the way it normally is, then we have to seek ways to recover it. This also happens to such entities as hard disk drives on computers, compact discs, DVDs, RAID, storage tapes, and other forms of electronics.
Data loss typically comes about as a result of either physical damage to the device storing the data or else logical damage done to the device's file storage system. The latter type of damage results in the data being unable to be mounted by the host's operating system.
The term "data recovery" may also refer to the process wheree information that has been deleted is retrieved and secured from a storage system for forensic purposes.
Physical damage can afflict storage media in a variety of fashions. For one thing, a compact disc storing pertinent data can be affected by having one of its layers or its metallic substrate scraped off of it. Hard drive disks often experience mechanical failures, such as failed motors or head crashes. Quite often, tapes simply break down.
The problem with physical damage is that it always causes the loss of at least some – if not all data on the storage device. Sometimes the system's logical structures can be seriously damaged as well. Logical damage must be deal with immediately in order for any data recovery to occur.
It is much more common for logical damage to occur than physical damage. Most of the time, logical damage comes about as the result of a power outage, which will prevent the structures of the file system from being written to the desired storage media. As a result, the file system remains inconsistent. If your system is behaving in a strange fashion or crashes, you might lose some pertinent data that will have to be recovered. Thankfully, it is much easier to do this when it is a case of logical damage, rather than physical damage.