Chapter 6.5 Distributed File
Systems Summary
Junfei Wen Fall 2013
Outline
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6.1 Characteristics of DFS
6.2 DFS Design and Implementation
6.3 Transaction and Concurrency Control
6.4 Data and File Replication
Current Work
Future Work
6.1Characteristics of DFS
Dispersion
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Dispersed Files
Location Transparent
Location Independent
Dispersed Clients
login transparency
access transparency
Multiplicity
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Multiple Files
Replication Transparency
Multiple Clients
Concurrency Transparency
Others (general)
• Fault Tolerance – crash of server or client, loss of message
• Scalability – Incremental file system growth
• Efficient
6.2DFS Design and Implementation
• Hierarchy files structure
• File mounting protocol
– Explicit mounting, manual
– Boot mounting, boot up time mounting
– Auto mounting, mounting at use
• Distribute state information between server
and clients. Stateless or stateful server
• File access
– Space multiplexing, multiple copy of file
• Remote access
• Cache access
• Download/upload access
– Time multiplexing, concurrent control. Same file different time
• Simple RW
• Transaction
• session
• File sharing semantics
• Unix, update propagated immediately
• Session, delayed update
• Transaction, delayed update
COMPONENTS IN A FILE SYSTEM
6.3Transaction and Concurrency
Control
• Distribdute Transaction Processing System:
– Transaction Manager: correct execution of local
and remote transactions.
– Scheduler: schedules operations to avoid conflicts
using locks, timestamps and validation managers.
– Object Manager: coherency of replicas/caches;
interface to the file system.
• Serializability: A schedule is Serializable if the result
of execution is equivalent to that of a serial
schedule.
• Concurrency Control Protocol required to
maintain ACID Semantics for Concurrent
transactions.
– Two phase locking
– Timestamp ordering
– Optimistic
6.4Data and File Replication
• Architecture
• Client chooses one / more FSA to access data object.
• FSA acts as front end to replica managers RMs to
provide replication transparency.
• FSA contacts one or more RMs for actual updating
and reading of data objects.
• One-copy Serializability:
– The execution of transaction on replicated objects
is equivalent to the execution of the same
transactions on non-replicated objects
– Read Operations : Read-one-primary, Read-one
,Read-quorum
– Write Operations:Write-one-primary,Writeall,Write-all-available,Write-quorum,Write-gossip
• Quorum Voting : Uses Read Quorum, Write Quorum
– Write-write conflict: 2 * Write quorum > all object copies
– Read-write conflict: Write quorum + read quorum > all
object copies.
• Gossip Update Propagation:
– Read: if TSfsa<=TSrm, RM has recent data, return it,
otherwise wait for gossip, or try other RM
– Update :if Tsfsa>TSrm, update. Update TSrm send gossip.
Otherwise, process based on application, perform update
or reject
– Gossip : update RM if gossip carries new updates.
Current work
• A Distributed Cache for Hadoop Distributed
File System in Real-Time Cloud Service
• Intensive Workload Consolidation for the
Hadoop Distributed File Systems
• An integrated high-performance distributed
file system implementation on existing local
network
• A Cost-Effective File Lookup Service in a
Distributed Metadata File System
• The Mobile Agent-based Distributed Network
File system
Future work
• Innovations in the area of security for
Distributed/Cloud Computing
• Improve efficiency of Parallel/Distributed system
Concurrency control protocol
• Improve Efficiency and Effectiveness of file replication
scheme
• Integrate File Replication and Consistency
Maintenance
Reference
[1]Distributed Operating Systems and Algorithm Analysis,
Andy Chow & Theodore Johnson,1997
[2] “Optimizing File Replication over Limited-Bandwidth
Networks using Remote Differential Compression”
IEEE Infocom Conference, 2006.
[3] Transaction Management and Concurrency control by
Connolly & Begg. Chapter 19. Third edition
[4] "Distributed File System Replication: Frequently Asked
Questions";http://technet2.microsoft.com/WindowsSe
rver/en/library/f9b98a0f-c1ae-4a9f-972480c679596e6b1033.mspx?mfr=true
[5]http://blogs.cs.st-andrews.ac.uk/angus/2009/09/
[6]http://www.quora.com/Distributed-Systems/What-isthe-future-of-file-systems -Future of File Systems
Thank you！