Introduction to Cluster cluster

Source: http://www.ibm.com/developerworks/cn/linux/cluster/lw-clustering.html
simply put, a cluster (cluster) is a group of computers that provide users with a set of network resources as a whole. These individual computer systems are nodes of the cluster. An ideal cluster is that users never realize the underlying nodes of a clustered system, and in his/her view, the cluster is a system, not multiple computer systems. And the administrators of the cluster system can arbitrarily increase and revise the nodes of the cluster system.
cluster is not a new concept, in fact, as early as the 70 's computer manufacturers and research institutions began the research and development of cluster systems. These systems are not well known because they are mainly used in scientific engineering calculations. Until the advent of the Linux cluster, the concept of clustering was widely disseminated. Cluster system is mainly divided into high-availability (Hi availability) cluster, called HA Cluster, and high-performance computing (Perfermance Computing) cluster, referred to as HPC cluster.
The cluster system (Cluster) mainly addresses the following issues:
1. High reliability (HA). With the cluster management software, when the primary server fails, the backup server can automatically take over the work of the primary server and switch the past in time to realize uninterrupted service to the users.
2. High Performance Computing (HP). That is to make full use of the resources of each computer in the cluster to realize the parallel processing of complex operations, which is usually used in scientific computing fields, such as gene analysis, chemical analysis, etc.
3. Load Balancing. That is, the load pressure is allocated to each computer in the cluster according to some algorithm, in order to relieve the pressure of the primary server and reduce the hardware and software requirements of the primary server.
Scientific Clusters
In General, the first involves developing parallel programming applications for clustering to solve complex scientific problems. This is the basis for parallel computing, although it does not use a dedicated parallel supercomputer, which consists of 10 to tens of thousands of independent processors. However, it uses a commercial system, such as a group of single-processor or dual-processor PCs linked by a high-speed connection, and communicates on the public message-passing layer to run parallel applications. As a result, you will often hear about the advent of a cheap Linux supercomputer. But it is actually a computer cluster with the same processing power as a real supercomputer, usually a decent set of cluster configuration overhead of more than $100,000. This may seem too expensive for the average person, but it is cheaper than a dedicated supercomputer worth millions of dollars.
Load Balancing cluster
The load Balancing cluster provides a more practical system for enterprise requirements. As the name implies, the system allows the load to be distributed as evenly as possible in the computer cluster. The load may be a load or network traffic load that requires balanced application processing. Such a system is ideal for a large number of users running the same set of applications. Each node can handle a portion of the load, and the load can be dynamically allocated between nodes to achieve balance. This is true for network traffic as well. Typically, a Web server application accepts too many network traffic so that it cannot be processed quickly, which requires sending traffic to a network server application running on another node. It can also be optimized based on the different available resources on each node or the special environment of the network.
High Availability cluster
The High availability cluster appears to make the overall service of the cluster as usable as possible in order to consider computational hardware and software error-prone. If the primary node in the high availability cluster fails, it will be replaced by the secondary node during that time. Secondary nodes are typically mirrors of the primary node, so when it replaces the primary node, it can take over its identity completely, and thus make the system environment consistent with the user.
between these three basic types of clustering, mixing and mixed often occur. As a result, a high availability cluster can also be found to balance the user load between its nodes while still trying to maintain high levels of availability. Similarly, a parallel cluster can be found in the cluster to be programmed into the application, and it can perform load balancing between nodes. Although the cluster system itself is independent of the software or hardware it is using, the hardware connection plays a key role in effectively operating the system.
Introduction to Microsoft Windows 2003 cluster
A server cluster is a set of stand-alone servers that work together and run Microsoft Cluster Services (Microsoft Cluster Service,mscs). Server clusters provide high availability, failure recovery, scalability, and manageability for resources and applications.
server clusters allow clients to access applications and resources while they are in failure and scheduled pauses. If one of the servers in the cluster is unavailable because of a failure or maintenance requirement, the resources and applications are transferred to the available cluster nodes.
The Windows Clustering (Windows Clustering) solution uses the term "high availability" rather than "fault tolerance." Fault-tolerant technology provides a higher level of resiliency and resiliency. Fault-tolerant servers typically use deep hardware redundancy, plus specialized software, to recover virtually any single hardware or software error in almost instant. These solutions are much more expensive than Windows Clustering (Windows Clustering) solutions because organizations must pay for redundant hardware that is waiting for errors in idle state.
server clusters cannot guarantee uninterrupted operation, but they do provide sufficient availability for most mission-critical applications. The Cluster service monitors applications and resources and can automatically identify and recover numerous failure conditions. This provides the flexibility to manage workloads in a cluster. In addition, the availability of the entire system is improved.
the benefits of Cluster service (Cluster services) include:
• High Availability: Ownership of resources (for example, disk drives and Internet Protocol (IP) addresses) is automatically transferred from the failed server to the available servers through a server cluster. When a system or application in a cluster fails, the cluster software restarts the failed application on the available servers or disperses the work from the failed node to the remaining nodes. As a result, the user only senses the pause of the service in an instant.
• Failback: When the failed server returns to its intended preferred owner's online status, the Cluster service will automatically reassign the workload in the cluster. This feature is configurable, but is disabled by default.
• Manageability: You can use the Cluster Administrator tool (CluAdmin.exe) to manage the cluster as a single system and to administer the application as if it were running on a single server. You can transfer applications to other servers in the cluster. Cluster Administrator can be used to manually balance the workload of the server and release the server for scheduled maintenance. You can also monitor the status of the cluster, all nodes, and resources from anywhere on the network.
• Scalability: The Cluster service can scale to meet demand growth. Additional nodes can be added when the overall load of the cluster-supervised application is beyond the capabilities of the cluster.

Introduction to Cluster cluster