Linux Virtual Server - Purpose and Function

Purpose and Function

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: is an advanced IP load balancing software implemented inside the Linux kernel. The IP Virtual Server code was already included into the standard Linux kernel 2.4 and 2.6.
  • KTCPVS: implements application-level load balancing inside the Linux kernel, currently under development.

Users can use the LVS solutions to build highly scalable and highly available network services, such as web, email, media services and VoIP services, and integrate scalable network services into large-scale reliable e-commerce or e-government applications.

The LVS solutions have already been deployed in many real applications throughout the world, including Wikipedia.

The LVS component depends upon the Linux Netfilter framework and its source code is available in the net/netfilter/ipvs/ subdirectory within the kernel source. It implements several balancing schedulers, listed below with the relevant source file:

  • Round-Robin (ip_vs_rr.c)
  • Weighted Round-Robin (ip_vs_wrr.c)
  • Least-Connection (ip_vs_lc.c)
  • Weighted Least-Connection (ip_vs_wlc.c)
  • Locality-Based Least-Connection (ip_vs_lblc.c)
  • Locality-Based Least-Connection with Replication (ip_vs_lblcr.c)
  • Destination Hashing (ip_vs_dh.c)
  • Source Hashing (ip_vs_sh.c)
  • Shortest Expected Delay (ip_vs_sed.c)
  • Never Queue (ip_vs_nq.c)

List retrieved from http://www.linuxvirtualserver.org/docs/scheduling.html

The module 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 tool is ipvsadm.

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