This is the third in a series of newsletters that is exploring our premise that we are returning to a new generation of mainframe computing. With that in mind, this newsletter will continue the discussion that was started in the last newsletter about how thin clients are the modern day equivalent of the dumb ASCII and IBM 3270 terminals of the previous mainframe era. In particular, this newsletter will discuss server side virtualization. This newsletter will also ask, and answer, the oft asked question: how thin can you get?
Snow White and the Seven Dwarfs
With server-side virtualization, the client device plays the familiar role of a terminal accessing an application or a desktop hosted on a central presentation server, similar to how a dumb terminal or a 3270 terminal used to access an IBM 360 series of computer during the previous generation of mainframe computing. One of the advantages of server-side virtualization, vs. client-side virtualization, is that the application can more easily be securely accessed from home PCs, airport Internet kiosks, smartphones, and other thin client devices.
There are two primary approaches to the current generation of server-side virtualization. They are Server Based Computing (SBC) and Virtual Desktop Infrastructure (VDI). IT organizations have been using the SBC approach to virtualization for a long time and often refer to is as Terminal Services, which again is reminiscent of the previous generation of dumb terminals. VDI is a relatively new variation on the overall server-side form of virtualization where a virtual machine (VM) on a central server is dedicated to host a single virtualized desktop. Both SBC and VDI are getting a lot of attention from IT organizations because of their promise of providing a combination of cost savings, increased ability to comply with myriad regulations and an improvement in data and application security.
This, however, is where the similarities between the previous era of mainframe computing and the current environment split direction. They split direction over the network. The mainstay of the WAN that supported the first generation of mainframe computing was a 9600 baud, analog, multi-point private line. That quite literally meant that a single analog private line, running at 9600 baud, terminated in a data center in one city and connected offices in multiple cities. In addition, the traffic patterns were so predictable that there was a widely used algorithm, the Esau-Williams Algorithm that was used to design the WAN.
In our next newsletter we will discuss how the WAN that supports the emerging era of mainframe computing is totally different than the WAN that supported the previous era. And in terms of the question we raised about how thin can you get, the answer is very, very thin. The emerging era of mainframe computing is sometimes supported not by thin clients, but by zero clients. These are user display devices that have no operating system and no processor.