Add the Texas-based RackSpace to the long list of international tech companies opening research and development facilities in Israel. Last week, the company acquired Israeli start-up ZeroVM, which has developed a virtual server system, called a hypervisor, specifically for cloud use. With the acquisition, ZeroVM’s Tel Aviv office will be turned into RacksSpace’s Israeli R&D center. The terms of the deal were not disclosed.

RackSpace, which started out as a hosting company for websites, has over the years evolved into a major cloud operation, offering online users numerous tools that enable them to develop their products using RackSpace’s platform. With ZeroVM, RackSpace will be able to offer customers a major upgrade on speed and deployment, thanks to the built-for-the-cloud architecture ZeroVM offers.

In order to ensure that their programs run smoothly, software developers need to work on different operating systems. Buying separate servers for the dozens of operating systems out there is prohibitively expensive, so developers use virtual operating systems — called hypervisors — to duplicate the environment in which they need to work. Numerous companies, such as VMWare, Citrix, Oracle and others, produce hypervisors that enable developers to work in these different environments.

For start-ups, though, even the money-saving strategy of doing all their development work on one server is expensive, and old-fashioned. Instead of investing in server equipment, the modern way of development is via the cloud. It’s a lot cheaper to rent time on a cloud server, like Amazon EC2 or Google Cloud Platform, than to buy servers. The emergence of cloud development environments over the past several years has been a boon for companies large and small, and especially for new start-ups. It gives companies access to top-flight equipment and development tools for a fraction of what it would cost to buy them.

There’s only one problem with this setup, according to Constantine Perespykin, a co-founder, along with Camuel Gilyadov, of ZeroVM: If you need a hypervisor for development, you can’t be in the cloud. “The current architecture of the cloud is fundamentally broken, because it relies on hypervisors that were made for on-site servers. The world has moved on to cloud, but hypervisors haven’t,” Perespykin said.

One of the advantages of cloud computing is that it allows developers to use only the components of operating systems or development tools that they actually need. It’s because of that ability to pick and choose — loading into their virtual memory just the portions of, for example, a heavyweight computer-aided design tool that they need to use, instead of the whole huge program with all its features — that cloud development is even possible. If the entire suite of CAD tools had to be run at the same time, things would slow down considerably, souring developers on the cloud very quickly.

For one reason or another, that kind of nimble deployment passed over the hypervisor world, and attempting to use one online is an exercise in futility, said Perespykin. Hypervisors in the cloud are the same as they are on local servers, and their architecture does not allow them to be “modularized,” cloud-style.

That applies to all hypervisors, except the one developed by ZeroVM, Perespykin said. “We have developed a hypervisor that allows developers to load just the parts of the operating system that they need to work with their applications. “ZeroVM only virtualizes the server parts that do the actual work,” he said.

The secret: ZeroVM’s technology builds a virtual server out of portions of the Linux library that can be used to emulate operating systems, detecting the components of an OS that an application needs and emulating it. Instead of the many megabytes a traditional hypervisor “weighs,” ZeroVM requires about 75 kb of memory — a minuscule amount. The result: instead of the two minutes or so a traditional cloud-based hypervisor would need to deploy itself, ZeroVM takes less than 5 milliseconds, or about 1/20000th of that time.

It’s that lightness and speed that RackSpace likes about ZeroVM, the company said when it announced the purchase. “ZeroVM is efficient because it is made to virtualize applications, not machines. The runtime virtualizes only the server parts that do the actual work at hand, making it much faster,” RackSpace said. “Making things smaller, lighter and faster also provides greater security. An optimization expert once said something to the effect that ‘You can’t make computers go faster; you can only make them do less.’ That’s the value of ZeroVM,” said RackSpace.