Book excerpt: This IBM® RedpaperTM publication is a comprehensive guide that covers the IBM Power System S821LC (8001-12C) server that uses the latest IBM POWER8® processor technology and supports the Linux operating system (OS). The Power S821LC server is designed to maximize data center floor space with its dense 1U server design, which helps to reduce infrastructure cost. The Power S821LC server delivers superior performance and exceptional throughput for data center and cloud workloads that require dense virtualization, open source database deployment, and high-performance computing applications. The Power S821LC server supports up to two processor sockets, offering 16-core 2.328 GHz (3.026 GHz turbo) or 20-core 2.095 GHz (2.827 GHz turbo) POWER8 configurations in a 19-inch rack-mount, 1U (EIA units) drawer configuration. All the cores are activated. The objective of this paper is to introduce the Power S821LC offering and its relevant functions, including: Two POWER8 processors in a 1U form factor Dense virtualization and dense database deployment capability-providing more value per server footprint than 1U x86-based alternatives Leadership data throughput that is enabled by POWER8 multithreading with up to 4X more threads than x86 designs Superior application performance due to 2x per core performance advantage over x86-based systems Acceleration of a broad range of workloads with GPUs and superior I/O bandwidth with Coherent Accelerator Processor Interface (CAPI) This publication is for professionals who want to acquire a better understanding of IBM Power SystemsTM products. The intended audience includes the following roles: Clients Sales and marketing professionals Technical support professionals IBM Business Partners Independent software vendors This paper expands the current set of IBM Power Systems documentation by providing a desktop reference that offers a detailed technical description of the Power S821LC system.