Load Balancing

DATA AND SERVICES AVAILABITLITY:

LOAD BALANCING
PRESENTED BY:
FARES BEN HAMOUDA
JAWHER JOUINI
Network & System Administration

November 2015

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OUTLINES

• INTRODUCTION
• DEFINITION OF THE CONCEPT OF « LOAD BALANCING »
• LINUX VIRTUAL SERVER (LVS)
• IMPLEMENTATION OF THE LVS FRAMEWORK
• DEMO

Network & System Administration

November 2015

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INTRODUCTION (MAIN ISSUES)

Network & System Administration

November 2015

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INTRODUCTION (REQUIREMENTS)

• NEW REQUIREMENTS IN ORDER TO PRESERVE THE AVAILABILITY OF DATA
AND SERVICES:
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INCREMENTAL SCALABILITY
24X7 AVAILABILITY
MANAGEABILITY
COST-EFFECTIVENESS

Network & System Administration

November 2015

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LOAD BALANCING
• USED TO SPREAD WORK BETWEEN MANY COMPUTERS, PROCESSES, DISKS OR OTHER RESOURCES
IN ORDER TO GET OPTIMAL RESOURCE UTILIZATION (MAXIMIZE THROUGHPUT), DECREASE
COMPUTING TIME (MINIMIZE RESPONSE TIME), AND AVOID OVERLOAD OF ANY SINGLE RESOURCE
• TO INCREASE THE CAPACITY OF A SERVER FARM BEYOND THAT OF A SINGLE SERVER.
• IT CAN ALSO ALLOW THE SERVICE TO CONTINUE EVEN IN THE FACE OF SERVER DOWN TIME DUE TO
SERVER FAILURE OR SERVER MAINTENANCE.
• A LOAD BALANCER CONSISTS OF A VIRTUAL SERVER (IP ADDRESS + PORT).
• VIRTUAL SERVER IS BOUND TO A NUMBER OF PHYSICAL SERVICES RUNNING ON THE PHYSICAL
SERVERS IN A SERVER FARM.
• A CLIENT SENDS A REQUEST TO THE VIRTUAL SERVER THAT SELECTS A PHYSICAL SERVER IN THE
SERVER FARM AND DIRECTS THIS REQUEST TO THE SELECTED PHYSICAL SERVER.

Network & System Administration

November 2015

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LOAD BALANCING
• LOAD BALANCERS ALSO PERFORM SERVER MONITORING OF SERVICES IN
A WEB SERVER FARM.
• IN CASE OF FAILURE OF ALL THE SERVERS BOUND TO A VIRTUAL SERVER,
REQUESTS MAY BE SENT TO A BACKUP VIRTUAL SERVER (IF
CONFIGURED) OR OPTIONALLY REDIRECTED TO A CONFIGURED URL.
• IN GLOBAL SERVER LOAD BALANCING (GSLB) THE LOAD BALANCER
DISTRIBUTES LOAD TO A GEOGRAPHICALLY DISTRIBUTED SET OF SERVER
FARMS BASED ON HEALTH, SERVER LOAD OR PROXIMITY.
Network & System Administration

November 2015

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LOAD BALANCING
• LOAD BALANCING METHODS:
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LEAST CONNECTIONS
ROUND ROBIN
LEAST RESPONSE TIME
LEAST BANDWIDTH
DOMAIN NAME HASHING
SOURCE IP ADDRESS

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DESTINATION IP ADDRESS
SOURCE IP - DESTINATION
STATIC PROXIMITY, USED FOR GSLB
LEAST PACKETS
URL HASHING

Network & System Administration

November 2015

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