LVS load balancing mode --NAT

Cluster Application Overview

Meaning cluster

Cluster, clusters, cluster
It consists of multiple hosts, but only outside the performance as a whole

Cluster Category

According to the target cluster for which differences can be divided into three types

Load-balancing clusters
High Availability Cluster
High Performance Computing Cluster

Load-balancing clusters (Load Balance Cluster)

The ability to increase the impact of the application of the system, as far as possible to handle more access requests, reduce latency as the goal, to achieve high concurrency, high-load (LB) overall performance
LB load distribution dependent on the primary node split algorithm

High availability cluster (High Availability Cluster)

To improve the reliability of the application system, the terminal reduces the time target as possible, to ensure continuity of service, to achieve high availability (HA) fault tolerance effect
HA works includes a duplexer and two ways from the main

High-performance computing clusters (High Performance Computer Cluster)

To improve the application system CPU speed, scalable hardware resources and analytical capacities, to obtain the equivalent of a large, high-performance supercomputer computing (HPC) capabilities
High performance is dependent on the high-performance computing cluster "distributed computing", "parallel operation", by dedicated hardware and software integrated CPU, memory, and other resources of the plurality of servers, realized only large, supercomputers only have the computing power

Load balancing cluster mode of analysis

Load balancing cluster is the most used business cluster model
of the cluster load scheduling technique has three operating modes

Address Translation
IP tunnel
Direct Routing (DR Mode)

NAT mode - NAT (Network Address Translation)

Referred to as the NAT mode, similar to the structure of the private network firewall, load balancer as a gateway to all of the server node, that is, as a client to access the entrance, as well as access nodes in response to export client
Private IP address of the server node, and a load balancer located in the same physical network, security is better than the other two methods

About virtual server LVS
Linux Virtual Server

For load balancing scheme of the Linux kernel

LVS load scheduling algorithm

Polling (Round Robin)

The access request received in turn in the order assigned to each node in the cluster (real server), uniformly treat each server, regardless of the actual number of connections and the server system load

WRR (Weighted Round Robin)

The processing capacity of real servers in turn allocate access requests received, the query scheduler may automatically load each node and dynamically adjusts its weight
Ensure strong server processing power to take on more traffic

LVS load scheduling algorithm

Least Connection (Least Connections)

Allocated according to the number of connections the real server is established, access will receive priority in the allocation requests to the node with the fewest number of connections

Weighted least connections (Weighted Least Connections)

In the big difference in performance server node, the weights may be re-adjusted automatically real server

Higher weights node will assume a greater proportion of the activities connected load

Experimental Environment Description:
1. the LVS server, WEB server dispatch two
2.WEB server 1 installed apache service
3.WEB server 2, the service installation apache
4. The server provides a storage space to achieve NFS shared storage function
5. Support machine as a test LVS polling query features

Roles	IP
1.LVS	ens33: 192.168.100.1 ens36: 12.0.0.1
2.WEB1	192.168.100.10
3.WEB2	192.168.100.20
4.NFS	192.168.100.100

A. Configure the NFS Service

Check whether to install rpcbind and nfs-utils package

rpm -q nfs-utils
rpm -q rpcbind


没有安装则用
yum install nfs-utils rpcbind -y

Create a mount directory

mkdir /opt/kgc
mkdir /opt/accp

Configuring NFS shared storage space

vim /etc/exports
/opt/kgc	192.168.100.0/24(rw,sync,no_root_squash)
/opt/accp	192.168.100.0/24(rw,sync,no_root_squash)

NFS feature is turned on, turn off the firewall

systemctl start nfs
systemctl start rpcbind
systemctl stop firewalld.service 

//查看共享空间
showmount -e
Export list for nfs:
/opt/accp 192.168.100.0/24
/opt/kgc  192.168.100.0/24

II. Configuring two Apache Service

kgcWEB service configuration

yum install httpd -y

//修改kgcWEB服务监听地址
vim /etc/httpd/conf/httpd.conf
Listen:192.168.100.10:80

//创建首页内容
vim /var/www/html/index.html
<h1>this is kgc web</h1>

//挂载NFS共享存储空间
kgcWEB
vim /etc/exports
192.168.100.100:/opt/kgc	/var/www/html	nfs	defaults,_netdev 0 0
mount -a

accpWEB service configuration

yum install httpd -y

//修改accpWEB服务监听地址
vim /etc/httpd/conf/httpd.conf
Listen:192.168.100.20:80

//创建首页内容
vim /var/www/html/index.html
<h1>this is accp web</h1>

//挂载NFS共享存储空间
accpWEB
vim /etc/exports
192.168.100.100:/opt/accp	/var/www/html	nfs	defaults,_netdev 0 0
mount -a

Shut down two servers firewall

III. Configuring the LVS Service

Installation services ipvsadm

yum install ipvsadm -y

As a gateway, routing forwarding need to open

//开启路由转发功能
vim /etc/sysctl.conf
net.ipv4.ip_forward=1
systemctl -p

Add iptables rules to set the address mapping

iptables -F
iptables -t nat -F
iptables -t nat -A POSTROUTING -o ens36 -s 192.168.100.0/24 -j SNAT --to-source 12.0.0.1

LVS load the kernel module

modprobe ip_vs

Open ipvsadm

ipvsadm --save > /etc/sysconfig/ipvsadm

Open LVS Service

systemctl start ipvsadm.service

LVS rule script writing

vim /opt/nat.sh
#!/bin/bash
ipvsadm -C                //初始化
ipvsadm -A -t 12.0.0.1:80 -s rr
ipvsadm -a -t 12.0.0.1:80 -r 192.168.100.10 -m   //调度服务器
ipvsadm -a -t 12.0.0.1:80 -r 192.168.100.20 -m  //调度服务器
ipvsadm