Replication == each machine holds all files
load balancing, availability fault tolerance
writes become more complex
-> synchronously to all
-> or, write to one, then propagated to others
replicas must be reconsiled
Partitioning
== each machine has subset of files
availability vs. single server DFS
scalabililty w/file system size
single file write simpler
on failure, lose portion of data load balancing harder; if not balanced, then hot spots possible
NFSv3 == stateless, NFSv4 == stateful
caching
session-based(non-concurrent)
periodic updates
– default: 3sec for files; 30 sec for dir
NFSv4 => delegation to client for a period of time(avoids ‘update checks’)
locking
lease-based
NFSv4 => also “share reservation” – reader/writer lock
Access Pattern (workload) analysis
-33% of all file accesses are writes
