Smoothing a discrete world

For the short term (until we sell one) there are three cars in my household. A manual transmission, an automatic and a CVT (continuous variable transmission). This makes me uniquely qualified to write about Cloud Computing.

That’s because Cloud Computing is yet another area in which the manual/automatic transmission analogy can be put to good use. We can even stretch it to a 4-layer analogy (now that’s elasticity):

Manual transmission

That’s traditional IT. Scaling up or down is done manually, by a skilled operator. It’s usually not rocket science but it takes practice to do it well. At least if you want it to be reliable, smooth and mostly unnoticed by the passengers.

Manumatic transmission (a.k.a. Tiptronic)

The driver still decides when to shift up or down, but only gives the command. The actual process of shifting is automated. This is how many Cloud-hosted applications work. The scale-up/down action is automated but, still contingent on being triggered by an administrator. Which is what most IaaS-deployed apps should probably aspire to at this point in time despite the glossy brochures about everything being entirely automated.

Automatic transmission

That’s when the scale up/down process is not just automated in its execution but also triggered automatically, based on some metrics (e.g. load, response time) and some policies. The scenario described in the aforementioned glossy brochures.

Continuous variable transmission

That’s when the notion of discrete gears goes away. You don’t think in terms of what gear you’re in but how much torque you want. On the IT side, you’re in PaaS territory. You don’t measure the number of servers, but rather a continuously variable application capacity metric. At least in theory (most PaaS implementations often betray the underlying work, e.g. via a spike in application response time when the app is not-so-transparently deployed to a new node).


OK, that’s the analogy. There are many more of the same kind. Would you like to hear how hybrid Cloud deployments (private+public) are like hybrid cars (gas+electric)? How virtualization is like carpooling (including how you can also be inconvenienced by the BO of a co-hosted VM)? Do you want to know why painting flames on the side of your servers doesn’t make them go faster?

Driving and IT management have a lot in common, including bringing out the foul-mouth in us when things go wrong.

So, anyone wants to buy a manual VW Golf Turbo? Low mileage. Cloud-checked.


Filed under Application Mgmt, Automation, Cloud Computing, Everything, IT Systems Mgmt, Utility computing

4 Responses to Smoothing a discrete world

  1. Ah, but VW Golf T or Tdis work best with both manual transmission and forward planning: drop a gear before the dashed lines in the middle of the road say it’s OK to pull out and the engine is spun up before you need the extra power. Something to do with latency.

    It’s a two-phase commit process, except with French drivers, where the optimistic commit algorithm “nobody will be coming round the blind corner” applies.

  2. William,

    What CVT vehicle do you own. A DAF?


  3. Steve: now you know why my wife decided that’s the car we’re selling.

    Roger: a Prius. Yes, I know a Prius doesn’t have a true CVT since the transmission has to intermediate between 2 engines and the wheels, not just one engine. But I didn’t want to get too technical in this simplistic analogy, and the Prius transmission exhibits the same property of not having discrete gears which is the only relevant aspect in this context.

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