Replication File Replication systems are really just one manifestation of replicated persistent data. We will talk about replicated files in the rest of this section, but the concepts are generally applicable to other objects, including parts of files. There are a number of techniques that are used to provide replication, and they each have their costs and benefits. A file may be made more available in the face of failures of a file server if it appears on more than one file server.
Availability is one of the main measures of the advantage of a replication algorithm.
Performance - if a file is 'nearer' a user, access will generally be faster. Files may be replicated across local storage devices at creation time, or they may be 'cached' when first accessed. Portability - file access should be possible after a workstation is detached from the network if portability is required. Replication carries with it several overheads. Whole file copies are relatively expensive Consistency of Updates.