Priority Estimation Tool (PrIeST)<\/a> to capture our data and ratings. The example data used in this article can be downloaded and imported in PrIeST.<\/p>\nThe first step in AHP now is to compare pairs of criteria and specify their importance to each other. This comes down to ratings like: The criterion cost is three times more important than availability. Decisions like this need to be made for all pairs of criteria. The rating is done on a numeric scale from 1 to 9, on which 1 means both criteria are of equal importance and 9 means one dominates the other. After the rating is done, PrIeST will present the resulting priorities. This shows, which influence each criterion has in reaching our goal.<\/p>\nCriteria weights.<\/figcaption><\/figure>\nThe same pairwise comparison needs to be done for each criterion and all alternatives. In this case we need to determine the capabilities of each provider in a certain area and also rate it on a scale from 1 to 9. The concrete ratings can be found in the attached file and are based on the following facts:<\/p>\n
Availability is an easy one, because all three providers offer the same quantity: 99,99%. This means, that a VM can be unavailable for 4,38 hours per year. Although the service quality is the same between all three, they offer different discounts when violating the SLA.<\/p>\n
To better compare the costs, a basic scenario was matched against the three providers:<\/p>\n
\n3 Web Server VMs (4 Cores, 16GB RAM, 100GB storage)<\/li>\n 3 Database VMs ( 2 Cores, 16GB RAM, 1TB storage)<\/li>\n 100GB In\/Out traffic<\/li>\n<\/ul>\nTo sum up, Google was by far the cheapest of the three competitors. Their prices were only half of Amazon’s and Microsoft’s which leads to the weights below.<\/p>\n
Functionality is a tricky one, because here the providers differ very much. To keep it simple, services are first classified by themes (network, databases, Big Data, etc.) and then compared between the providers. Results are then aggregated in three categories:<\/p>\n
\nServices offered by all providers<\/li>\n Services offered by some providers<\/li>\n Services offered by one provider (unique)<\/li>\n<\/ul>\nAll providers offer basic services like virtual machines, containers, network services (DNS, VPN, Load-Balancers, \u2026) or databases, while IoT (Internet of Things) services are only provided by Amazon and Microsoft. To sum up, Amazon offered six unique services while Google and Microsoft each only offered one.<\/p>\n
The criterion Sizing is based on the number and range of supported instance types. Amazon offers many instance types (29) where customers can choose between 1\u201332 CPUs and 0.5\u2013244 GB RAM. Google only offers 18 different types with 1\u201332 CPUs and 0.6\u2013208GB RAM. A unique feature of Google is the ability to specify a custom instance in the given range of resources. Microsoft offers 25 different instance types where you can choose between 1\u201316 CPUs and 0.75\u2013112GB RAM.<\/p>\n
Amazon offers two european datacenters in Ireland and Frankfurt (a third is planned) and offers 50\/56 services in Ireland and 36\/56 services in Frankfurt. Google runs one datacenter in Belgium and 15 of 17 services can be hosted there. Microsoft currently runs two datacenters (Ireland, Netherlands) and offers 60\/90 and 71\/90 services there.<\/p>\nAll ratings of the alternatives.<\/figcaption><\/figure>\nTo get startet with PrIeST, we’ll import the example data and calculate the result. To start it, use the following command or just doubleclick PriEsTGUI.jar<\/p>\n
> java -jar PriEsTGUI.jar<\/pre>\nNow press Import and select the example.pwc file. Under Problem and Details you can find the alternatives and criteria as well as the numeric ratings of the pairwise comparison. To calculate the result select Eigenvector in the Methods panel and click Rebuild All. The results can now be found in the top right corner and are presented in the figure below.<\/p>\nFinal ratings.<\/figcaption><\/figure>\nWe can see that Amazon and Google fulfill our goal equally, while Microsoft is far behind.<\/p>\n