As described in part 1 of this blog series, the cloud is not the answer for every enterprise or every workload. This is true based on the current economics even without considering additional factors like security, control and SLA’s. On the other hand the economics do point out a major cloud advantage when it comes to short term or variable workloads. ( pointed out by Michael Keen and Billy Marshal as well ) Perhaps this is not very surprising to many, but it does help to look at the numbers to put it in perspective. The largest Intrinsic cost advantage of the Cloud is the ability to share infrastructure among multiple customers ( i.e. Multi-Tenancy and/or Multi-Instance ). This comes into play when many customers have variable workloads that are not likely to overlay at the same time. A Cloud infrastructure can load balance this workload on-demand significantly reducing the cumulative infrastructure required to support N number of customer workloads.

A Premise only solution will typically deploy the infrastructure required to accommodate the anticipated peak demand plus a factor of safety. As a result excess capacity is built into every deployment even if it is rarely ( or never ) utilized. This formula gets very expensive for many scenarios such as implementing a redundant DR solution across multiple data centers or a retailer building infrastructure to accommodate the Christmas shopping season but paying for it all year. As noted in the Cloud 101 example however, when a premise based is well utilized it can be the most cost effective solution to stay with especially if the on-site facilities can accommodate the anticipated growth.

The following Premise Plus Cloud scenario provides an optimized view of where a fully utilized premise infrastructure is used for constant predictable workloads and the Cloud is used for the variable workload. To put some simple numbers to it based on the original example, let’s assume that the constant workload is roughly equal to 5 Quadcore server capacity. The variable workload on the other hand peaks at 160% of the base requirement, however it is required only about 400 hours per year, which could translate to 12 hours a day for the month of December or 33 hours per month for peak loads such as test or batch loads. The cost for a premise only solution for this situation comes to roughly 2X or $ 15,600 per year assuming existing space and a 20% factor of safety above peak load. If on the other hand you were able to utilize a Cloud for only the peak loads the incremental cost would be only $1,000. ( Based on Amazon EC2 )

Premise Only
$ 15,600 Annual cost ( 2 x 7,800 from Part 1 )
Premise Plus Cloud
$ 7,800 Annual cost from Part 1
$ 1,000 Cloud EC2 – ( 400 x .8 x 3 )
$ 8,800 Annual Cost Premise Plus Cloud

As noted for this example the server cost of using a Premise Plus Cloud solution could save as much as 44%. This does not factor in many costs that either the Premise only scenario or Premise Plus Cloud would face but those costs vary according to the situation. So the challenge is how to identify variable workloads that can be placed in the Cloud or split between premise and cloud. The CSP ( Cloud Service Provider ) must also provide the proper infrastructure and remote administration to enable corporate IT to control and manage applications and images in the extended cloud as a virtual private network of their own. Economics aside, the CSP also needs to address the SLA’s and security concerns that corporate IT has identified as prerequisites for adoption. Given the intrinsic cost savings possible as portrayed in this example, there is little doubt that CSP’s will fill the gaps and the industry will move to Premise Plus Cloud solutions.

Part 1 – Premise vs Cloud vs Colo

Part 3 – Reserved Pricing

Part 4 – Amazon EC2 vs Terremark vCloudPart 5 – Amazon EC2 Micro AMI