A lot has been said about the wonders of workload VM portability.
Within the construct of virtualization, and especially VMware, an awful lot of time is spent on VM Mobility but as numerous polls and direct customer engagements have shown, the majority (50% and higher) do not use VMotion. I talked about this in a post titled “The VM Mobility Myth:”
…the capability to provide for integrated networking and virtualization coupled with governance and autonomics simply isn’t mature at this point. Most people are simply replicating existing zoned/perimertized non-virtualized network topologies in their consolidated virtualized environments and waiting for the platforms to catch up. We’re really still seeing the effects of what virtualization is doing to the classical core/distribution/access design methodology as it relates to how shackled much of this mobility is to critical components like DNS and IP addressing and layer 2 VLANs. See Greg Ness and Lori Macvittie’s scribblings.
Furthermore, Workload distribution (Ed: today) is simply impractical for anything other than monolithic stacks because the virtualization platforms, the applications and the networks aren’t at a point where from a policy or intelligence perspective they can easily and reliably self-orchestrate.
That last point about “monolithic stacks” described what I talked about in my last post “Virtual Machines Are the Problem, Not the Solution” in which I bemoaned the bloat associated with VM’s and general purpose OS’s included within them and the fact that VMs continue to hinder the notion of being able to achieve true workload portability within the construct of how programmatically one might architect a distributed application using an SOA approach of loosely coupled services.
Combined with the VM bloat — which simply makes these “workloads” too large to practically move in real time — if one couples the annoying laws of physics and current constraints of virtualization driving the return to big, flat layer 2 network architecture — collapsing core/distribution/access designs and dissolving classical n-tier application architectures — one might argue that the proposition of VMotion really is a move backward, not forward, as it relates to true agility.
That’s a little contentious, but in discussions with customers and other Social Media venues, it’s important to think about other designs and options; the fact is that the Metastructure (as it pertains to supporting protocols/services such as DNS which are needed to support this “infrastructure 2.0″) still isn’t where it needs to be in regards to mobility and even with emerging solutions like long-distance VMotion between datacenters, we’re butting up against laws of physics (and costs of the associated bandwidth and infrastructure.)
While we do see advancements in network-driven policy stickiness with the development of elements such as distributed virtual switching, port profiles, software-based vSwitches and virtual appliances (most of which are good solutions in their own right,) this is a network-centric approach. The policies really ought to be defined by the VM’s themselves (similar to SOA service contracts — see here) and enforced by the network, not the other way around.
Further, what isn’t talked about much is something that @joe_shonk brought up, which is that the SAN volumes/storage from which most of these virtual machines boot, upon which their data is stored and in some cases against which they are archived, don’t move, many times for the same reasons. In many cases we’re waiting on the maturation of converged networking and advances in networked storage to deliver solutions to some of these challenges.
In the long term, the promise of mobility will be delivered by a split into three four camps which have overlapping and potentially competitive approaches depending upon who is doing the design:
- The quasi-realtime chunking approach of VMotion via the virtualization platform [virtualization architect,]
- Integration distribution and “mobility” at the application/OS layer [application architect,] or
- The more traditional network-based load balancing of traffic to replicated/distributed images [network architect.]
- Moving or redirecting pointers to large pools of storage where all the images/data(bases) live [Ed. forgot to include this from above]
Depending upon the need and capability of your application(s), virtualization/Cloud platform, and network infrastructure, you’ll likely need a mash-up of all three four. This model really mimics the differences today in architectural approach between SaaS and IaaS models in Cloud and further suggests that folks need to take a more focused look at PaaS.
Don’t get me wrong, I think VMotion is fantastic and the options it can ultimately delivery intensely useful, but we’re hamstrung by what is really the requirement to forklift — network design, network architecture and the laws of physics. In many cases we’re fascinated by VM Mobility, but a lot of that romanticization plays on emotion rather than utilization.
So what of it? How do you use VM mobility today? Do you?