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Load balancing

Load balancing

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Load balancing

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  1. Loadbalancing Dawid Królak

  2. Intro • Problem • Model OSI • Layer 2 • Layer 4-7 • Reverse Proxy

  3. Problem How to maintainlargeamount of queries, requests? Buy a newfaster, batter hardware?Buy fasterlinks? Reduce service? Useloadbalancingmethods!

  4. Advantages • Use hardware that is available but unused at this time. • Use cheaper hardware. • First properly configured easier to upgrade, maintain. • Scalability. • It`s all about speed.

  5. Disadvantages • Difficult to configure. • Need more IT knowledge.

  6. Levels of LoadBalancing • Layer 2 OSI Model (Link aggregation) • Layer 4 OSI Model (TCP/UDP) • Layer 7 OSI Model (Reverse Proxy)

  7. Model OSI Application Presentation Session Transport Network Data Link Physical

  8. Data link – linkaggregation • Many physicallinkscan be seen as one logical. • Defined by IEEE 802.3ad standard.

  9. Caution! Standard IEEE 802.3ad is not definingLoadBalancing! To loadbalancing we need to usealgorithms! But without link aggregation we can`t talk aboutlayer 2 loadbalancing.

  10. Link Aggregation Features: • LoadSharing (usingavailablelinks) • Automatic configuration • Deterministic (predictable, controllable) • Frame order (frame order ispreserved)

  11. Limiations • We need to useadditionalalgorithms to useloadbalancing • Works only between two devices. • Same speed on links (should be).

  12. Additionalinfo Somealgorhithmscan be foundat: • http://www.google.sk/search?q=layer+2+load+balancing+algorithms

  13. Layer 4 loadbalancing • Layer-4 load balancing is to distribute requests to the servers at transport layer, such as TCP, UDP and SCTP transport protocol. • We know one address, loadbalancerisswitchingus to one of many servers. • Pure 4-layer loadbalancingisbeingdisplacing by layer4-7 loadbalancing.

  14. Layer4-7 loadbalancing Problems: • One service can be run on multiple logical machines. • Logicalmachinecan be builtfrom many physicalmachines. Main role of load balancing is to distributerequests to multiple logic machines/services.

  15. Layer 4-7 loadbalancing Advantages: • Scalability • We canscalethat part of system that we need. • Nowadays many serversaresupportingthis. (database, www, webservices, dns)

  16. Layer 4-7 loadbalancing

  17. Reverseproxy • Reverseproxyisspecialserverproxytype. • Typically set at front of webservers. • Thisproxycandistributeconnections to a differentaddress. • Fast and easy to configurein popular webservers(apache, lighttp)

  18. LoadBalancinglayer 2-4-7 • Loadbalancing 2 and 4-7 can be usedatthe same time. • Loadbalancercandistributerequests to otherloadbalancer • Loadbalancingisusedincloudcomputing. • Loadbalancer and services can be runnedat one physical and logicalmachine, likecasual PC /but thereis no sense to do it/ • It`sbetter to set someloadbalancersinstead of buyingnewbetterfaster and moreexpensive hardware.

  19. Bibliography http://wiki.hill.com/wiki/index.php?title=IEEE_802.3ad http://books.google.pl/books?id=SF_LzThJdB0C http://kb.linuxvirtualserver.org/wiki/Load_balancing

  20. Finish. Any Questions? Thankyou for yourattention. Ďakujemza pozornosť. Dziękuję za uwagę.