VISHWESHWARAYA TECHNOLOLOGICAL UNIVERSITY, BELGAUM.

Clusters

Yasir H WaniM.Tech, VTU

An approach to provide:

• High Performance• High Availability

Server Application

What is clustering?

“A cluster is a group of interconnected, whole computers working together as a unified computing resource that can create an illusion of being one single machine.”

• Whole Computer? What the heck is that???

• How would a cluster then look like?

Definition:

NASA 128-processor Beowulf cluster: A cluster built from 64 ordinary PC's.

• Absolute Scalability• Incremental Scalability• High Availability• Superior price/performance (Google mantra!)

But same is achieved if SMP is used! How is it different then? (We will see later)

Benefits /Objectives/Design Requirements

• High speed link is used to exchange messages for coordination of cluster activity

Figure: Standby Server with no shared disk)

Cluster Configuration 1

• Use of RAID (Redundant Array of Independent Disks; originally Redundant Array Of Inexpensive Disks)

Shared disk

Cluster Configuration 2

• One computer handle all the processing load• Other computer remains inactive (for backup)

What about coordination?• Primary system periodically sends “ heart beat” message• Increased Availability, but same old Performance Not at all Clustering coz :-

I. Not maintaining the image of Single System to outside world.II. “All are actively doing process” not followed.

1: Passive Standby

Clustering Approaches

• Each computer is a Separate Server• Private disk is maintained• High performance and high availability• Scheduling software needed to schedule tasks among sep. ser.• Load balancing provided

(Q): How availability?Data is constantly copied among systems to maintain current state of data in all the systems. Disadv: Comes at cost of performance penalty.

2: Separate ServerClustering Approaches continued…

• Each volume is owned by a single computer• If a system fail, volume ownership changes

Shared Disk

All computers have access to all the systems

• This requires some locking facility

Common disks partitioned into volumes & each system given a volume

Shared Nothing

• Failure management • Load Balancing• Parallelizing Computation

a. Compiler time

b. At Application layer via Message Passing

c. Parametric Computing E.g. Simulation

Enhancement to the single system OS

Operating System Issues

Cluster middleware Duties/Functional Components:• job management system• cluster monitoring system• parallel libraries• automatic client installation systems• cluster management tools• distributed and parallel file systems• global process space

Cluster middleware is a set of programs which provide SSICluster Middleware

Cluster Computer Architecture

1) Cluster-Based Scalable Network Services -Armando Fox Steven D. Gribble Yatin Chawathe Eric A. BrewePaul Gauthier, University of California at Berkeley

2) Operating Systems- Internals and Design Principles(6th Edition) by William Stalling

3) http://www.scfbio-iitd.res.in/doc/clustering.pdf4) http://en.wikipedia.org/wiki/Cluster_computing \5) http://www.cro-ngi.hr/en/technologies/cluster-technologies/

References: