Linux Cluster Technology _unix Linux

At present, more and more websites adopt Linux operating system, and provide services such as mail, Web, file storage, database and so on. There are also a number of companies that use Linux servers to provide these services within the intranet. With the deepening of people's reliance on Linux servers, the reliability, load capacity and computing power are also paid more attention. The Linux cluster technology came into being, which can meet people's needs at low cost. One of the reasons Linux is competitive is that it can run on very popular PCs without the need to buy expensive dedicated hardware devices. On several PCs running Linux, as long as the corresponding cluster software, can be composed of super reliability, load capacity and computing power of the Linux cluster. Each server in a cluster is called a node. Depending on the focus, the Linux cluster can be divided into three categories. One is a high-availability cluster that runs on two or more nodes, with the aim of continuing to provide services in the event of certain failures in the system. The idea of a high-availability cluster is to minimize service outage times. This kind of cluster is more famous for Turbolinux Turboha, Heartbeat, kimberlite and so on. The second category is a load-balancing cluster, which is designed to provide load capacity that is proportional to the number of nodes, and is ideal for Web services that provide large traffic. Load-balanced clusters often have some high availability features. Turbolinux Cluster Server, Linux Virtual server are load-balanced clusters. The other is the Supercomputing cluster, which can be divided into two types according to the different degree of calculation. One kind is the task slice way, wants to divide the computation task into the task slice, then assigns the task slice to each node, calculates each node separately and then summarizes the result, produces the final computation result. The other is a parallel computing method, in which the data are exchanged in a large amount in the computation process, and can be calculated with strong coupling relationship. These two supercomputing clusters are suitable for different types of data processing work respectively. With supercomputing cluster software, companies can use a number of PCs to complete computing tasks that are usually only supercomputers. This kind of software has turbolinux enfusion, score and so on. The high availability cluster and the load Balancing cluster work in different ways and are suitable for different types of services. Typically, load-balancing clusters are suitable for services that provide static data, such as HTTP services, while high-availability clusters are suitable for services that provide static data, such as HTTP services, and services that provide dynamic data, such as databases. High-availability clusters can be applied to services that provide dynamic data because nodes share the same storage media, such as Raidbox. That is, within a high-availability cluster, the user data for each service is only one, stored on a shared storage device, and at any one time onlyA node can read and write this data. In the case of Turbolinux Turboha, there are two nodes A and b in the cluster, which provide only Oracle services, and user data is stored on the partition/DEV/SDB3 of the shared storage device. In normal state, Node A provides Oracle database services, and partition/DEV/SDB3 is loaded on/mnt/oracle by Node A. When a system fails and is detected by the Turboha software, Turboha stops the Oracle service and unloads the partition/dev/sdb3. After that, the Turboha software on Node B loads the partition on Node B and starts the Oracle service. There is a virtual IP address for the Oracle service, and when the Oracle service switches from Node A to Node B, the virtual IP address is also bound to Node B, so the user can still access the service. As can be seen from the above analysis, the high availability cluster does not have load balancing function for a service, it can improve the reliability of the whole system, but can not increase the load capacity. Of course, a high-availability cluster can run multiple services and be allocated appropriately on different nodes, such as Node A, which provides Oracle services, while Node B provides Sybase services, which can also be seen as a sense of load balancing, but it is for the allocation of multiple services. Load-balancing clusters are useful for services that provide relatively static data, such as HTTP services. Because typically there is no shared storage medium between nodes of a load-balanced cluster, user data is replicated in multiple copies and stored on each node that provides the service.