GFS Consistency Model
Learn how the Google File System achieves file consistency through its custom model for write operations and record appends. Understand defined, undefined, and inconsistent regions in file data and discover techniques applications use to handle GFS’s relaxed consistency. Compare GFS with HDFS to see different approaches in distributed file mutation.
GFS provides a custom consistency model for write operations.
The state of a file region after a mutation depends on the type of mutation, whether it succeeds or fails and whether there are concurrent mutations.
Note: A file region is consistent if all clients will always see the same data, regardless of the replica they read from.
A region within a file
A region is defined after a file data mutation if it is consistent and clients will see what the mutation writes in its entirety.
A region can be:
- Defined and consistent: When a mutation succeeds without interference from concurrent writes, the affected region is defined. All clients will always see what the mutation