Virtually Physical

Did I mention, how much I like solving math problems? No? Maybe because I don’t, actually.

This weeks puzzle to be solved: How big can our hosted virtual machines get without blocking too many resources and what can we do in case they still need to grow?

Historically VMs where created to consolidate all these tiny little server loads lurking in our data centers. each one on its own hardware that was essentially never utilized at all. Today these VMs get bigger and bigger every year as hypervisors can allocate more and more resources to each virtual machine. But there is a limit after all.

The Host server can only handly so much load. At a certain point of growth it simply doesn’t make sense to host a super large VM, since there will be only enough resources for 2 or three of them. We could now revert to a physical installation, but this would also rob us of some ofthe benefits we had with the virtual machines. Like: moving the server from host to host for maintenance, business continuity in case a host server fails, easy backups through storage snapshots of the image file, etc.

And after all… we would still have the same SLA with out clients, so we all would likely have to install a physical failover cluster to keep up out agreements. No, I don’t want to go there anymore!

Why don’t we just boot the hardware directly from the virtual disk? Windows 7 and Server 2008 have this feature build in, for most of the other OS’ there are tools that help you.

Only one catch: Native support in Windows seems only to support the VHD format while VMWare provides me with a VMDK. There are some tools that enable you to boot any kind of image, but I really need to figure out how to do this in an highly automated production environment.

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