1. Nache: Design and Implementation of a Caching Proxy for NFSv4
Bo Zhao
Computer Science and Engineering
The Pennsylvania State University

2. Motivation Enterprises are moving toward distributed operations
Sharing files across office location in wide area
Sharing data
In a uniform, secure, and consistent manner
Across the global enterprise
Reasonably good performance.

3. Related Work NFS and CIFS - work for a LAN
Low latency and high bandwidth
AFS and DCE/DFS – work for a WAN
Uniting disparate file servers into a single logical file system.
Deployment expense – not widely adopted
GPFS or Lustre - high performance & strong consistency
Expensive or difficult to deploy and administer

4. Cache Consistency NFS – close-to-open consistency
Open – check file attribute
Close – write back pending changes
No distributed cache coherency or concurrent write management
AFS – rely on client-side caching for performance
Callback to notify the client of updates
Close – changes become visible at the server

5. Cache Consistency CIFS – strong cache consistency - OpLocks Exclusive
Not need communicate with server before close
Batch
Hold on to the oplock after close
Level II
Read only

6. New features of NFS v4 COMPOUND RPC
Many NFS operations in a single RPC call
Lower overall network delay
Client redirection
Client can be redirected to another server
Build servers in distributed wide Area
OPEN delegations
Eliminates: client checking with the server for cache consistency.

7. Read Delegation OPEN, CLOSE and READ requests Handled locally.
All READs
without sending GETATTRs to check cache validity
All LOCK requests
sent to the server
Callback path is established for recalling a delegation

8. Performance of Read Delegation

9. Write Delegation
All OPEN, READ, WRITE, CLOSE, LOCK, GETATTR, SETATTR requests
Handled locally
On a conflicting OPEN by another client
The server recalls the delegation
Client commits all dirty data and return the delegation.

10. Performance of Write Delegation

11. Nache vs Redirection In federated system
Data on different geographically distributed physical locations,
Two models for data access
Client redirection
Data shipping

12. System Architecture

13. Nache Architecture
the Nache proxy sits in between a local NFS client and a remote NFS server caching the remote data closer to the client. Nache acts as an NFS server to the local client and as an NFS client to the remote server.

14. Performance of Read and Write Delegations

15. Benefits of Nache

16. Effect of Proxy on response time over a WAN