You have to understand where you have come from in order to know where you are going. In this section, you are going to look at how the IT world started in the mainframe era and is now moving toward cloud computing. Youâll also learn why this is relevant to Windows Server 2012 Hyper-V.
Computing of the Past: Client/Server
How computing has been done has changedâand in some ways, almost gone full circleâover the past few decades. Huge and expensive mainframes dominated the early days, providing a highly contended compute resource that a relatively small number of people used from dumb terminals. Those mainframes were a single and very expensive point of failure. Their inflexibility and cost became their downfall when the era of client/server computing started.
Cheap PCs that eventually settled mostly on the Windows operating system replaced the green-screen terminal. This gave users a more powerful device that enabled them to run many tasks locally. The lower cost and distributed computing power also enabled every office worker to use a PC, and PCs appeared in lots of unusual places in various forms, such as a touch-screen device on a factory floor, a handheld device that could be sterilized in a hospital, or a toughened and secure laptop in a military forward operating base.
The lower cost of servers allowed a few things to happen. Mainframes require lots of change control and are inflexible because of the risk of mistakes impacting all business operations. A server, or group of servers, typically runs a single application. That meant that a business could be more flexible. Need a new application? Get a new server. Need to upgrade that application? Go ahead, after the prerequisites are there on the server. Servers started to appear in huge numbers, and not just in a central computer room or datacenter. We now had server sprawl across the entire network.
In the mid-1990s, a company called Citrix Systems made famous a technology that went through many names over the years. Whether you called it WinFrame, MetaFrame, or XenApp, we saw the start of a return to the centralized computing environment. Many businesses struggled with managing PCs that were scattered around the WAN/Internet. There were also server applications that preferred the end user to be local, but those users might be located around the city, the country, or even around the world. Citrix introduced server-based computing, whereby users used a software client on a PC or terminal to log in to a shared server to get their own desktop, just as they would on a local PC. The Citrix server or farm was located in a central datacenter beside the application servers. End-user performance for those applications was improved. This technology simplified administration in some ways while complicating it in others (user settings, peripheral devices, and rich content transmission continue to be issues to this day). Over the years, server processor power improved, memory density increased on the motherboard, and more users could log in to a single Citrix server. Meanwhile, using a symbiotic relationship with Citrix, Microsoft introduced us to Terminal Services, which became Remote Desktop Services in Windows Server 2008.
Server-based computing was all the rage in the late 1990s. Many of those end-of-year predictions told us that the era of the PC was dead, and weâd all be logging into Terminal Servers or something similar in the year 2000, assuming that the Y2K (year 2000 programming bug) didnât end the world. Strangely, the world ignored these experts and continued to use the PC because of the local compute power that was more economical, more available, more flexible, and had fewer compatibility issues than datacenter compute power.
Back in the server world, we also started to see several kinds of reactions to server sprawl. Network appliance vendors created technologies to move servers back into a central datacenter, while retaining client software performance and meeting end-user expectations, by enabling better remote working and consolidation. Operating systems and applications also tried to enable centralization. Client/server computing was a reaction to the extreme centralization of the mainframe, but here the industry was fighting to get back to those heady days. Why? There were two big problems:
