1. Ch 11 Distributed File System
Ch11.1 Architecture
Srithi Reddy Muthyala
Oct

2. Three Archs to Introduce
Client-Server Arch (Centralized)
NFS (Network File System)
Cluster-based Arch (Less Centralized)
GFS (Global File System)
Symmetric Arch (Fully Distributed)
DHT-based (Distributed Hash Table)

3. Three Archs to Introduce
Client-Server Arch (Centralized)
NFS
Cluster-based Arch (Less Centralized)
GFS
Symmetric Arch (Fully Distributed)
DHT-based

4. Intro to NFS
2 ways of C-S Arch
Naive way.
RPC

5. Intro to NFS- basics
Although implemented by SUN Solaris, it is the predominant FS implementation on Unix System
Layered Structure
VFS: Virtual File System- Common Interface for Remote file and local
RPC: For data transport

6. NFS API Interfaces

7. Three Archs to Introduce
Client-Server Arch (Centralized)
NFS
Cluster-based Arch (Less Centralized)
GFS
Symmetric Arch (Fully Distributed)
DHT-based

8. Cluster-Based Distributed File Systems
Downsides of a C-S Arch
Performance bottle neck
Single-Point-Failure
Solution: Files(resources) can be stored on a few servers
A big file across multi servers
File Stripping for big structured files
Many files on different servers
Most files are not well structured

9. Cluster-Based Distributed File Systems
How to support file access in a Data Center?
Files permanently growing
File size might be multi gigabytes.
A server might be malfunction
File access request from any client should be responded in any condition

10. Cluster-Based Distributed File Systems

11. Cluster-Based Distributed File Systems
GFS, how does it work?
A cluster has a master node, which ONLY keeps meta information of files
A big file is splited into CHUNKS, a CHUNK of size 64Mbs.
Chunks are spread on many chunk servers
More details on GFS
Chunks are replicated --- Redundancy
Master does not keep up-to-date of chunk locations
A Chunks server knows what exactly it stores.
If client retrieval failed(low probability), ask Master again, master update latest info from chunk servers

12. Cluster-Based Distributed File Systems
GFS, how does it work?
File update. Client pushes back updated file chunk to corresponding chunk server
Chunk server conducts the backup/replication
Master node is kept out of this loop, bottle neck problem is solved
I/O performance of a GFS is pretty good and scalability is good as well

13. Three Archs to Introduce
Client-Server Arch (Centralized)
NFS(Network File System)
Cluster-based Arch (Less Centralized)
GFS ( Global File System)
Symmetric Arch (Fully Distributed)
DHT-based (Distributed Hash Table)

14. Symmetric Arch Peer-to-Peer No Client, No server, No Master, No Chunk
First realization is Ivy (Multi user Read/Write)

15. Symmetric Arch

16. What is a DHT? Hash Table data structure that maps “keys” to “values”
essential building block in software systems
Distributed Hash Table (DHT)
similar, but spread across many hosts
Interface
insert(key, value)
lookup(key)

17. Symmetric Arch Ivy details
Data storage. File composed of 8kb data blocks.
Content-hash data blocks
Public-key based blocks
Replication
Every block B is stored on K immediate successors, better availability

18. DHT: basic idea
K V
K V
K V
K V
K V
K V
K V
K V
K V
K V
K V
Operation: take key as input; route messages to node holding key

19. Future Developments Client-Server Arch (Centralized)
NFS
Cluster-based Arch (Less Centralized)
GFS
Symmetric Arch (Fully Distributed)
DHT-based

20. Reference
Ghemawat, Sanjay, Howard Gobioff, and Shun-Tak Leung. "The Google file system." ACM SIGOPS operating systems review. Vol No. 5. ACM, 2003.
Sandberg, Russel, et al. "Design and implementation of the Sun network filesystem." Proceedings of the Summer USENIX conference
Muthitacharoen, Athicha, et al. "Ivy: A read/write peer-to-peer file system." ACM SIGOPS Operating Systems Review 36.SI (2002):
Naor, Moni, and Udi Wieder. "A simple fault tolerant distributed hash table."Peer-to-Peer Systems II. Springer Berlin Heidelberg,
Cai, Min, Ann Chervenak, and Martin Frank. "A peer-to-peer replica location service based on a distributed hash table." Proceedings of the ACM/IEEE conference on Supercomputing. IEEE Computer Society, 2004.
Kleiman, Steve R. "Vnodes: An Architecture for Multiple File System Types in Sun UNIX." USENIX Summer. Vol