Some Musings on Virtual Machines

By Art Reisman

The other day, I sold a smart refrigerator  to a customer. When they found out it had a computer in it, and could be controlled remotely from the Internet, they asked me if they could run it on their Virtual Machine to save some space in the kitchen.  I told them, sure  we support that , they just need to get a-hold of  an  add-on compressor and a 40 foot cubic container module for their VM,  and we would just ship a plug-in application. There would be no need to ship any hardware to them, we have  a virtual refrigerator!

I purposely used that over the top analogy, to highlight,  the chill down my spine I feel, when I hear about vendors bundling their core network equipment into a VM.

Virtual machines make a lot of sense for somebody running a data center with 10 different servers and consolidating them into one box.   My underlying discomfort stems from the extension of  that mission onto equipment that is involved the real-time transport of your data.  Switches , routers , firewalls and bandwidth shapers.  Why do I feel this way? Am I just an old stubborn  engineer clinging to the old ways while the world passed me by?

Not really, we have set up virtual machines with our bandwidth shaper with success in our labs, it is actually pretty cool. My discomfort arises with the fact that bandwidth shapers are finely tuned, real-time devices, with software that must run at the core level of the computer’s operating system.  A bandwidth shaper must have absolute control of perhaps 4 ethernet/fiber ports or more and under no circumstances can it compete with  CPU resources should a server become overloaded.  The consequences of any resource contention are at best a slow internet, and at worst a complete lock up.   Yes I understand a in theory a modern VM can divvy up resources , but how do we ensure that it is done correctly ?   When we ship a standalone device running only our application we know  exactly what it is capable of,  and since we have thousands of identical configuration in the field,  we know that the technology configuration that leaves our factory dock is rock solid stable.

This is not to say we will never offer a virtual machine, we did have one customer where the logistics of their set up was so remote that the benefits of a virtual bandwidth  shaper on their standard configuration far outweighed the risks I mentioned above; but for the most part saving a few dollars on rack space and an extra piece of hardware are not worth the jeopardizing the stability of a critical piece of in-line equipment.



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