2. Simply put, one is to forward a large number of concurrent processing to multiple nodes in the back end to reduce the response time; The second is to forward a single heavy work to multiple nodes in the back end for processing, and then return it to the load balancing center and then to the users. At present, most load balancing technologies are used to improve the availability and scalability of Internet server programs, such as Web servers, FTP servers and other mission-critical servers.
1) Layer 2 load balancing (mac)
According to OSI model, Layer 2 load is generally in the form of virtual mac address, and external requests for virtual MAC address are distributed after load balancing.
2) Three-layer load balancing
Generally, virtual ip address is adopted. External requests for virtual IP addresses are allocated to actual IP address responses after load balancing.
3) Four-Layer Load Balancing (tcp)
On the basis of three times load balancing, the request is received by IP+ port and then forwarded to the corresponding machine.
4) Seven-layer load balancing (http)
Receive the request according to the virtual url or IP and host name, and then turn to the corresponding processing server.
1. Four-layer load balancing works in the four layers of the OSI model, namely the transport layer. Four-layer load balancing can only forward the request according to the destination address and source address in the message, but can't modify or judge the specific type of the requested resource, and then forward it to the server to process the request through the scheduling algorithm inside load balancing. Four-layer load balancing only provides a reliable connection from terminal to terminal and forwards the request to the back end. The connection is the same from beginning to end. LVS is a typical four-layer load balancing.
2. The seven-layer load balancing works in the seventh application layer of the OSI model, so the seven-layer load balancing can be based on the requested application layer information, such as allocation to the back-end server according to the requested resource type, rather than IP and port selection. The function of seven-layer load balancing is richer and more flexible, and it can also make the whole network more intelligent. As shown in the above figure, the connections (for client and server) at both ends of the seven-layer load balancing are independent.
3. In short, realize four-layer load balancing based on IP+ port. Seven-layer load balancing is realized through application layer resources.
1, strong load resistance. Strong load resistance and high performance, which can reach 60% of F5 hardware; Low memory and cpu resource consumption.
2. Working in the 4th layer of the network, it is forwarded by vrrp protocol (for distribution only), and the specific traffic is handled by the linux kernel, so it does not generate traffic.
2. It has good stability and reliability, and has its own perfect hot standby scheme; (e.g. LVS+Keepalived)
3. The application range is relatively wide, and it works on the fourth floor, so it can balance the load of all applications without considering the specific application to be processed;
4. Conventional processing is not supported, and static and dynamic separation cannot be carried out.
5. Support load balancing algorithms: rr (round robin), wrr (weighted round robin), lc (minimum connection) and wlc (minimum connection).
6. Complex configuration, strong dependence on the network and high stability.
1, which works at Layer 7 of the network, can do some diversion strategies for http applications, such as domain name and directory structure;
2.Nginx is less dependent on the network, and theoretically it can ping to perform the loading function;
3. The installation configuration of 3.Nginx is relatively simple, and the test is convenient;
4. It can also withstand high load pressure and is stable, and generally can support more than 10000 concurrent times;
5. The health check of the back-end server only supports port detection, not url detection.
6.Nginx's asynchronous processing of requests can help the node server reduce the load;
7.Nginx can only support http, https and Email protocols, and its applicability is poor.
8. It is not supported to reserve the session directly, but it can be solved by ip_hash.
9. Support load balancing algorithms: round robin, weight round robin and IP hash.
10 and Nginx can also be used as Web servers, that is, caching functions.
1, which supports two proxy modes, TCP (four layers) and HTTP (seven layers), and supports virtual hosts;
2. It can supplement some shortcomings of Nginx, such as session maintenance and Cookie guidance.
3. It will be helpful to detect the problems of servers that support url detection.
4. More load balancing strategies are implemented, such as dynamic cycle, weighted source hash, weighted URL hash and weighted parameter hash.
5. In terms of efficiency, HAProxy will have a better load balancing speed than Nginx.
6.HAProxy can load balance Mysql, detect and load balance DB nodes at the back end.
9. Support load balancing algorithms: Round-robin, Weight-round-robin, source (original address reservation), RI (request URL) and rdp-cookie (according to cookie).
10, it cannot be a Web server, that is, a cache.
The difference between 1, four-tier and seven-tier load balancing
2. The characteristics of four-tier and seven-tier load balancing and the comparison among Nginx, Haproxy and LVS.
3.linux load balancing summarizes the difference between four-tier load and seven-tier load.