Virtualization

For a new chapter in my ongoing series of talks and articles about browser performance I wanted to examine how key user experience metrics like page load time are dependent on available hardware resources. I prepared a VM and started my tests with a single CPU core and 2 GB of RAM, planning to gradually add more cores, more RAM and, eventually, a GPU. As it turned out, the latter is harder than anticipated.

I wish all my friends and readers a merry christmas and happy new year! I hope you like sepago’s annual Christmas comic. VXI: How a Customer With Real Scalability Problems Uses Virtualization(Click on the image for a full-size version)

Although humans in general and members of its subspecies “marketing manager” in particular tend to treat currently “hot” topics as new and revolutionary, they only rarely are. In fact, “new” should be considered as in “new wine in old bottles” rather than in “did not exist before”. Take virtualization. Although the topic of the day seems to be cloud computing, virtualization can probably still be called “hot” (especially since a cloud also is a kind of virtualization). But is it new? Judge for yourself: Below I have compiled a list of boring old technologies that employ virtualization.

Bugs and Annoyances ICA connections initiated over the ICA client object (ICO) SDK fail because 128-bit encryption cannot be enabled. Apparently, setting EncryptionLevelSession does not work. Annoyingly, this bug is more than a year old, was fixed in the ICA client 10.2 and reappeared in the current version 11.0. Bugs like this one are bad for the entire Citrix ecosystem, because they break cool tools like Citrix Quick Launch, xConnect and others I may not even know about. [Update 2009-09-30: this bug has been fixed in ICA client 11.2.]

With virtualization, lying has become respectable. Processors lie to user mode processes about memory addresses. Computers lie to operating systems about installed hardware. Storage systems lie to everybody about the location of data. The virtualization hype transforms honest down-to-earth systems into lying medusas.

Even with the most meticulous design, the day will come when your farm’s capacity is not sufficient any more. User numbers increase, applications become more resource-hungry and the amount of data to be handled increases steadily. So what do you do? Simply more of the same, i.e. buy more servers and add them to the farm? That is one way of increasing capacity, but it is not the only one and therefore may not be the best.

Some time ago I attended a presentation by a former VMware, now Microsoft employee who claimed that Hyper-V’s lack of Live Migration aka VMotion is not relevant at all. According to him, the only people vigorously demanding such a feature are consultants, never customers. At the time I thought: “What a silly marketing number this is. Microsoft does not have it, so they tell everyone that it is not really needed until they have it.”

I will start the new year with a small series on Windows x64 in which I will explain why 64-bit computing is not only necessary but inevitable. I will then go on to explain in detail where Windows x64 differs from the 32-bit versions and what that means for all those who are responsible for the design, operation, and support of 64-bit systems. All the while I will be focusing on terminal servers, but most facts and conclusions are valid for other system types, too.