5. Design Overview:
Component’s Monitoring
Reading and writing of data
Storing of huge data
Assumptions:
Interface:
Not POSIX compliant
Additional operations
o Snapshot
o Record append
8. Single Master , Chunk size & Meta data
Single Master:
Minimal Master Load.
Fixed chunk Size.
The master also predicatively provide chunk
locations immediately following those requested by
unique id.
9. Single Master , Chunk size & Meta data
Chunk Size :
64 MB size.
Read and write operations on same chunk.
Reduces network overhead and size of metadata in
the master.
10. Metadata :
Types of Metadata:
o File and chunk namespaces
o Mapping from files to chunks
o Location of each chunks replicas
11. Chunk Locations:
o Master polls chunk server for the information.
o Client request data from chunk server.
Operation Log:
o Keeps track of activities.
o It is central to GFS.
o It stores on multiple remote locations.
12. System Interactions:
Write Operations
o Master picks one replica as primary.
o Primary defines serial order for
mutations.
o Replicas follow same serial order.
o Minimize management overhead at
the master.
13. Atomic Record Appends:
o GFS offers Record Append .
o Clients on di erent machines append to the sameff
file concurrently.
o The data is written at least once as an atomic unit.
14. Snapshot:
o It creates quick copy of files or a directory .
o Master revokes lease for that file
o Duplicate metadata
o On first write to a chunk after the snapshot operation
o All chunk servers create new chunk
o Data can be copied locally
