1.2.2. Horizontal Scalability
Red Hat's efforts in improving the performance of Red Hat Enterprise Linux 6 focus on scalability. Performance-boosting features are evaluated primarily based on how they affect the platform's performance in different areas of the workload spectrum — that is, from the lonely web server to the server farm mainframe.
Focusing on scalability allows Red Hat Enterprise Linux to maintain its versatility for different types of workloads and purposes. At the same time, this means that as your business grows and your workload scales up, re-configuring your server environment is less prohibitive (in terms of cost and man-hours) and more intuitive.
Red Hat makes improvements to Red Hat Enterprise Linux for both horizontal scalability and vertical scalability; however, horizontal scalability is the more generally applicable use case. The idea behind horizontal scalability is to use multiple standard computers to distribute heavy workloads in order to improve performance and reliability.
In a typical server farm, these standard computers come in the form of 1U rack-mounted servers and blade servers. Each standard computer may be as small as a simple two-socket system, although some server farms use large systems with more sockets. Some enterprise-grade networks mix large and small systems; in such cases, the large systems are high performance servers (for example, database servers) and the small ones are dedicated application servers (for example, web or mail servers).
This type of scalability simplifies the growth of your IT infrastructure: a medium-sized business with an appropriate load might only need two pizza box servers to suit all their needs. As the business hires more people, expands its operations, increases its sales volumes and so forth, its IT requirements increase in both volume and complexity. Horizontal scalability allows IT to simply deploy additional machines with (mostly) identical configurations as their predecessors.
To summarize, horizontal scalability adds a layer of abstraction that simplifies system hardware administration. By developing the Red Hat Enterprise Linux platform to scale horizontally, increasing the capacity and performance of IT services can be as simple as adding new, easily configured machines.
1.2.2.1. Parallel Computing
Users benefit from Red Hat Enterprise Linux's horizontal scalability not just because it simplifies system hardware administration; but also because horizontal scalability is a suitable development philosophy given the current trends in hardware advancement.
Consider this: most complex enterprise applications have thousands of tasks that must be performed simultaneously, with different coordination methods between tasks. While early computers had a single-core processor to juggle all these tasks, virtually all processors available today have multiple cores. Effectively, modern computers put multiple cores in a single socket, making even single-socket desktops or laptops multi-processor systems.
As of 2010, standard Intel and AMD processors were available with two to sixteen cores. Such processors are prevalent in pizza box or blade servers, which can now contain as many as 40 cores. These low-cost, high-performance systems bring large system capabilities and characteristics into the mainstream.
To achieve the best performance and utilization of a system, each core must be kept busy. This means that 32 separate tasks must be running to take advantage of a 32-core blade server. If a blade chassis contains ten of these 32-core blades, then the entire setup can process a minimum of 320 tasks simultaneously. If these tasks are part of a single job, they must be coordinated.
Red Hat Enterprise Linux was developed to adapt well to hardware development trends and ensure that businesses can fully benefit from them. Section 1.2.3, “Distributed Systems” explores the technologies that enable Red Hat Enterprise Linux's horizontal scalability in greater detail.
