LVS study notes 1-LVS introduction

LVS background

LVSThe project is developed by a free software project 1998年5月established by Dr. Wensong Zhang in China Linux Virtual Server, mainly for Linuxthe development of server clusters. At the same time, the Linux Virtual Serverproject is one of the earliest free software projects in China.

Linux Virtual ServerThe goal of the project: to use cluster technology and Linux operating system to achieve a high-performance, highly available server, it has a very good 可伸缩性（Scalability）, 可靠性（Reliability）and 可管理性（Manageability）.

Currently, the LVSproject has provided a Linux Virtual Serverframework for implementing scalable network services , as 图3shown. In the LVSframework, virtual server software with three IPload balancing technologies , core switches based on content request distribution, and cluster management software are provided. The framework can be used to realize highly scalable, highly available and other network services; on this basis, highly scalable and highly available e-commerce applications that support a large number of users can be developed.IPIPVSLayer-7KTCPVSLVSWeb、Cache、MailMedia

LVS overall architecture

The overall architecture is as follows:

Figure 1: LVS general three-tier architecture

Generally speaking, the LVScluster adopts a three-tier structure, and its system structure is as 图1shown. The main components of the three-tier are:

• Load balancer, which is the front-end machine of the entire cluster to the outside, is responsible for sending customer requests to a group of servers for execution, and customers think that the service comes from an IP address (we can call it a virtual IP address) Up.
• Server pool (server pool) is a set of servers that actually execute client requests. The executed services include WEB, MAIL, FTP, DNS, etc.
• Shared storage, which provides a shared storage area for the server pool, so that it is easy to make the server pool have the same content and provide the same services.

Scheduling methods applicable to different services:

• WEBservice:VS/NAT
• 媒体service:VS/DR
• Cacheservice:VS/TUN

The specific scheduling method will be explained in detail in the next article

IPVS components

• Part of the ipvs
  Linuxkernel, according to the rules to perform the requested scheduling, similar to Iptabelsthe netfilterkernel module! Linux 2.4Incorporate into the kernel during the version.
• ipadm
  is ipvsa command line tool for setting rules and needs to be installed and applicable.

ipvsWe only need to apply the general architecture to the above 2module!

IPVS cluster features

• Powerful

1. 3Kind of IPload balancing technology
2. 8Connection scheduling algorithm
3. Virtual service unlimited
4. Detailed statistics
5. Attack defense strategy

• Strong applicability

1. The back-end server can run any operating system that supports TCP/IP, including Linux, various Unix (such as FreeBSD, Sun Solaris, HP Unix, etc.), Mac/OS and Windows NT/2000, etc.
2. The load scheduler can support most TCP and UDP protocols:
   tcp: http、tcp、proxy、smtp、https、ldap
   udp:dns、ntp以及音视频协议

• performance

1. The cluster can support millions of concurrent
2. TUNOr DRtechnology, throughput can be close to10G/s

• reliability

1. LVSThe server cluster software has been well applied in many large and critical sites, so its reliability has been well confirmed in real applications. There are many schedulers running for more than a year without a restart.

• Software license

1. LVSCluster software is GPL（GNU Public License）free software released under license, which means that you can get the source code of the software and have the right to modify it, but you must ensure that your modifications are also GPLdistributed in a way.

to sum up

This article mainly introduces about LVSthe background and LVScharacteristics. For the detailed load balancing technology and scheduling algorithm we will explain in detail in the next article!

lvs社区Links to several articles you can refer to at the same time are as follows:

http://www.linuxvirtualserver.org/zh/lvs1.html
http://www.linuxvirtualserver.org/zh/lvs2.html
http://www.linuxvirtualserver.org/zh/lvs3.html
http://www.linuxvirtualserver.org/zh/lvs4.html