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What is the Cluster?

Before getting to the cluster it is worth discussing what a cluster is and some of the terminology. First, let's discuss the difference between a CPU and a GPU.

CPU -- Central Processing Unit

  • A CPU can never be fully replaced by a GPU
  • Can be thought of as the taskmaster of the entire system, coordinating a wide range of general-purpose computing tasks

GPU -- Graphics Processing Unit

  • GPUs were originally designed to create images for computer graphics and video game consoles
  • Performing a narrower range of more specialized tasks

You'll notice that in the picture above the CPU is composed of a smaller unit, a core. A core is the computing unit in a CPU. You'll also note that the whole system (including CPUs, GPUs and Storage) is a single computer in the system called a node.

When a CPU performs some computation they use a storage hierarchy. This hierarchy places small/fast storage options close to the CPU and slower/larger options away from the CPU. These small/fast options are called memory/RAM while the slower/larger options are simply called storage.

Now that we now the components we can put together an image of what a computer cluster is. A computer cluster is a group of loosely or tightly connected computers that work together as a single system. A HPC (High Performance Compute) cluster is a computer cluster capable of performing computations at high speeds.