The virtual data center, nomadic virtual machines.

Tonight I’ve been reading about security implications of migrating virtual machines between physical hosts in the data center cloud. I think this is far from the awful problem the authors make it out to be.

Live migration of virtual machines between hosts in a cloud provides large benefits in reliability. Migration allows virtual machines to be moved from hosts requiring maintenance, they can be moved to avoid imminent disaster, or moved to balance loads across the cloud. This gives us maximum uptime and the most consistent performance for the virtual machines.

The first objection to this migration is to insure the migrated virtual machine retains all of its security settings, storage access, and etc. This is a bit of a red herring to me. These are either things under control of the virtual machine (the cloud hosts couldn’t manipulate them anyways) or they are things that, if wrong, wouldn’t allow the virtual machine to continue to run. Not a security risk by any means.

The second objection is that any facilities such as load balancers have to know the virtual machine migrated. Not at all. Considering Xen Cloud Platform (which we use for our cloud), virtual machines retain their IP settings and the MAC addresses of their virtual interfaces. No external system has any idea whatsoever which virtual machine is running on which physical cloud host, or even which are virtual machines or physical machines. It’s all completely transparent.

Since no outside application that interfaces with the virtual machine, be it load balancer, firewall, etc has any way of knowing where the virtual actually lives in the cloud, there’s nothing to migrate when the virtual migrates.

The cloud does indeed demand uniformity of the equipment in it, but that has nothing to do with migrating virtuals and everything to do with basic cloud functionality. XCP, for example, will not permit physical hosts to join the cloud unless they match in terms of CPU, memory, and Ethernet ports. It doesn’t matter who the vendor is or even that the hardware is an across the board full match as long as those items match.

Migrating virtual machines isn’t as hard as you might think.

Vern, SwiftWater Telecom

virtual data center cloud service


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