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Can you help me with my capacity planning?

I would like to scale a web application to the Cloud and wanted to know if anyone had any experience calculating costs and could tell me how I would go about that. I have NO experience with cloud services at all.

Currently my production environment consists of two web servers and one database server.

If the application continues on a linear growth path, eventually, I want to scale to the cloud to avoid any more long term commitments to extra hardware.

I want to be able to create a similar environment I have now as a baseline. Have this as my fixed cost that I will always have.

I also want to calculate my variable costs that will increase with more users or bandwidth.

I don't have a preferred cloud vendor. Amazon, Rackspace, Terremark or any other is fine as long as understand how to calculate my fixed and variable costs.

marked as duplicate by EEAA, Michael Hampton, Chris S Sep 4 '12 at 2:20

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Calculating cloud-costs is simple on the surface, but complex once you get to the spread-sheets.

The simple part is you need to know 5 things:

  • How many servers you need
  • What their duty cycle is (probably 24/7 from the sounds of it)
  • What kind of IO you do
  • How much space you consume
  • What kind of bandwidth you need to the internet (or VPC if you're doing that)

Drop that into a spreadsheet with the cloud-provider's costs and you have your per-month costs.

The complex part comes in identifying those performance metrics, and working out the exact pricing strategy that works best for you. You already know server-count, and that's probably 90% of your total cloud-costs right there; three always-on servers are going to run you much, much more than you're likely to involve in the form of disk-space, disk-IO, and network throughput.

As for pricing, the cloud providers I know do allow different pricing schemes for rarely-on, sometimes-on, and always-on servers. Generally with a variable up-front cost and reduced hourly costs for the sometimes/always variants that come out to a significantly cheaper per-year cost than the straight-up hourly charge.

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