Overview: The SPD Engine

Using the SMP Computer

The SPD Engine exploits a hardware and software architecture known as symmetric multiprocessing. An SMP computer has multiple central processing units (CPUs) and an operating system that supports threads. An SMP computer is usually configured with multiple controllers and multiple disk drives per controller. When the SPD Engine reads a data file, it launches one or more threads for each CPU; these threads then read data in parallel from multiple disk drives, driven by one or more controllers per CPU. The SPD Engine running on an SMP computer provides the capability to read and deliver much more data to an application in a given elapsed time.

Reading a data set with an SMP computer that has 5 CPUs and 10 disk drives could be as much as 5 times faster than I/O on a single-CPU computer. In addition to threaded I/O, an SMP computer enables threading of application processes (for example, threaded sorting in the SORT procedure in SAS 9.1 or later).

The exact number of CPUs on an SMP computer varies by manufacturer and model. The operating system of the computer is also specialized; it must be capable of scheduling code segments so that they execute in parallel. If the operating system kernel is threaded, performance is further enhanced because it prevents contention between the executing threads.

As threads run on the SMP computer, managed by a threaded operating system, the available CPUs work together. The synergy between the CPUs and threads enables the software to scale processing performance. The scalability, in turn, significantly increases overall processing speed for tasks such as creating data sets, appending data, and querying the data by using WHERE statements.

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