Administrator's Guide to VMware Virtual SAN: Introduction to VSAN

Software-Defined Datacenter

VMworld, the VMware annual conferencing event, introduced VMware’s vision for the software-defined datacenter (SDDC) in 2012. The SDDC is VMware’s architecture for the public and private clouds where all pillars of the datacenter—compute, storage, and networking (and the associated services)—are virtualized. Virtualizing datacenter components enables the IT team to be more flexible. If you lower the operational complexity and cost while increasing availability and agility, you will ultimately lower the time to market for new services.

To achieve all of that, virtualization of components by itself is not sufficient. The platform used must be capable of being installed and configured in a fully automated fashion. More importantly, the platform should enable you to manage and monitor your infrastructure in a smart and less operationally intense manner. That is what the SDDC is all about! Raghu Raghuram (VMware senior vice president) captured it in a single sentence: The essence of the software-defined datacenter is “abstract, pool, and automate.”

Abstraction, pooling, and automation are all achieved by introducing an additional layer on top of the physical resources. This layer is usually referred to as a virtualization layer. Everyone reading this book is probably familiar with the leading product for compute virtualization, VMware vSphere. Fewer people are probably familiar with network virtualization, sometimes referred to as software-defined network (SDN) solutions. VMware offers a solution named NSX that is based on the solution built by the acquired company Nicira. NSX does for networking what vSphere does for compute. These layers do not just virtualize the physical resources but also allow you to pool them and provide you with an application programming interface (API) that enables you to automate all operational aspects.

Automation is not just about scripting, however. A significant part of the automation of virtual machine (VM) provisioning (and its associated resources) is achieved through policy-based management. Predefined policies allow you to provision VMs in a quick, easy, consistent, and repeatable manner. The resource characteristics specified on a resource pool or a vApp container exemplify a compute policy. These characteristics enable you to quantify resource policies for compute in terms of reservation, limit, and priority. Network policies can range from security to quality of service (QoS). Unfortunately, storage has thus far been limited to the characteristics provided by the physical storage device, which in many cases did not meet the expectations and requirements of many of our customers.

This book examines the storage component of VMware’s SDDC. More specifically, the book covers how a new product called Virtual SAN (VSAN), releasing with VMware vSphere 5.5 Update 1, fits into this vision. You will learn how it has been implemented and integrated within the current platform and how you can leverage its capabilities and expand on some of the lower-level implementation details. Before going further, though, you want to have a generic understanding of where VSAN fits in to the bigger software-defined storage picture.