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Distributed File Systems

Ivan P. Valarezo, Oct 2012 University of Melbourne - COMP90020
Motivation & goals
How do people store their info - the persistence schemes

Key aspects of data storage
other aspects related to data persistence
A typical Unix File System

DFS Requirements
The abstract model
Efficiency requirement
"At least the same power and generality as those found in a local FS" "share an expensive resource"

Access Transparency

Client programs does not need to know the exact storage location of a file
Performance transparency

Programs should perform well on loaded services
Location transparency

Uniform file name space
Mobility transparency

No changes for clients if data is moved
* service also could scale transparently
Concurrency requirement

Concurrent access to a file by different clients should be allowed

File Replication requirement
Ensures a consistent copy of a file across the service

HW and SO heterogeneity requirement

different operating systems and computers

Fault Tolerant requirement

protocol build around idempotent operations

Consistency requirement
one-copy update semantic

Security requirement
provide access control mechanisms

File Service Architecture
"Clean separation of the specific tasks in a DFS "

Quick comparison DFS and Unix FS

DFS Implementations

The NFS File System
From Sun's implementation up to now RFC 1813

Supported Requirements

Not fully supported

The NFS Architecture

NFS Architecture details


mount service details

The AFS File System
"Andrew File System - Transparent access to remote shared files for unix programs"


AFS Basic Operation

* vice process provides a callback promise, a guarantee to notify the client process when any other client modify the file.
AFS design assumptions


Other DFS solutions
Other works and recent developments



New DFS solutions
Recent works and Developments

GFS (Google File System)

New DFS solutions
Recent works and Developments

Gluster FS

see also

Amazon S3 PLAN 9 Sprite CIFS Network Attached Storages (NAS)

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