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Linux Virtual Server

linux virtual server, linux virtual server hosting
Linux Virtual Server LVS is load balancing software for Linux kernel–based operating systems

LVS is a free and open-source project started by Wensong Zhang in May 1998, subject to the requirements of the GNU General Public License GPL, version 2 The mission of the project is to build a high-performance and highly available server for Linux using clustering technology, which provides good scalability, reliability and serviceability


  • 1 Overview
    • 11 Schedulers
  • 2 Glossary
  • 3 Examples
  • 4 See also
  • 5 References
  • 6 External links


LVS as used by Wikimedia

The major work of the LVS project is now to develop advanced IP load balancing software IPVS, application-level load balancing software KTCPVS, and cluster management components

  • IPVS: an advanced IP load balancing software implemented inside the Linux kernel The IP Virtual Server code is merged into versions 24x and newer of the Linux kernel mainline
  • KTCPVS: implements application-level load balancing inside the Linux kernel, as of February 2011 still under development

LVS can be used for building highly scalable and highly available network services, such as web, email, media and VoIP services, and integrating scalable network services into large-scale reliable e-commerce or e-government applications LVS-based solutions already have been deployed in many real applications throughout the world, including Wikipedia

The LVS components depend upon the Linux Netfilter framework, and its source code is available in the net/netfilter/ipvs subdirectory within the Linux kernel source LVS is able to handle UDP, TCP layer-4 protocols as well as FTP passive connection by inspecting layer-7 packets It provides a hierarchy of counters in the /proc directory

The userland utility program used to configure LVS is called ipvsadm8, which requires superuser privileges to run


LVS implements several balancing schedulers, listed below with the relevant source files:

  • Round-robin ip_vs_rrc
  • Weighted round-robin ip_vs_wrrc
  • Least-connection ip_vs_lcc
  • Weighted least-connection ip_vs_wlcc
  • Locality-based least-connection ip_vs_lblcc
  • Locality-based least-connection with replication ip_vs_lblcrc
  • Destination hashing ip_vs_dhc
  • Source hashing ip_vs_shc
  • Shortest expected delay ip_vs_sedc
  • Never queue ip_vs_nqc


Commonly used terms include the following:

  • LVS director: load balancer that receives all incoming client requests for services and directs them to a specific "real server" to handle the request
  • Real servers: nodes that make up an LVS cluster which are used to provide services on the behalf of the cluster
  • Client computers: computers requesting services from the virtual server
  • VIP Virtual IP address: the IP address used by the director to provide services to client computers
  • RIP Real IP address: the IP address used to connect to the cluster nodes
  • DIP Directors IP address: the IP address used by the director to connect to network of real IP addresses
  • CIP Client IP address: the IP address assigned to a client computer, that it uses as the source IP address for requests being sent to the cluster


Setting up a virtual HTTP server with two real servers:

ipvsadm -A -t 19216801:80 -s rr ipvsadm -a -t 19216801:80 -r 1721601:80 -m ipvsadm -a -t 19216801:80 -r 1721602:80 -m

The first command assigns TCP port 80 on IP address 19216801 to the virtual server The chosen scheduling algorithm for load balancing is round-robin -s rr The second and third commands are adding IP addresses of real servers to the LVS setup The forwarded network packets shall be masked -m

Querying the status of the above configured LVS setup:

# ipvsadm -L -n IP Virtual Server version 108 size=65536 Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 19216801:80 rr -> 1721602:80 Masq 1 3 1 -> 1721601:80 Masq 1 4 0

See also

  • Computer networking portal
  • Linux portal
  • IP Virtual Server
  • Netfilter and nftables
  • Network scheduler


  1. ^ "IPVS Software - Advanced Layer-4 Switching" linuxvirtualserverorg 2011-02-08 Retrieved 2014-01-12 
  2. ^ Wensong Zhang 2011-02-08 "KTCPVS Software - Application-Level Load Balancing" Linuxvirtualserverorg Retrieved 2014-03-25 
  3. ^ "Job Scheduling Algorithms in Linux Virtual Server" linuxvirtualserverorg 2011-02-08 Retrieved 2013-11-24 
  4. ^ "Linux Virtual Server: Load Balance Your Networked Services" bobcarescom 2008 Retrieved 2013-11-24 

External links

  • Free software portal
  • Official website
  • Linux Virtual Server Configuration Wiki
  • IBM eServer BladeCenter, Linux, and Open Source: Blueprint for e-business on demand includes LVS as a component

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