So, let's say that you have an existing server that you'd like to migrate to Amazon's Elastic Computing Cloud (EC2) by using their physical to virtual (P2V) tool.  The question is, how much will this cost you for the initial Amazon Machine Image (AMI) upload to Amazon Simple Storage Server (S3)? And then, how much will it cost to continue to run on EC2?

The basic equation is relatively simple.  We'll go with an example, first.  Let's say you've got a server that's currently using 40GB of storage.  That will need to be packaged into an AMI.  Although there may be some compression (?) we'll assuming there isn't.  Uploading 40GB to S3 will cost 20 cents a gigabyte, or eight dollars (the costs are all in US dollars). After that, you'll be paying 15 cents a gigabyte per month to store this AMI or $6 per month plus bandwidth.  If you were using about 100GB a month of bandwidth, you'll be paying an addition $20 a month for that.  That's a total of $26 per month plus the cost of the instance at about $73 per month.  So, you'd then be paying about $99 per month.

However, if you just want to bring up your server in the cloud for a few hours to run some tests or experiments with different configurations, you'd only pay $8 to get it up there and then for the AMI time.

There is one caveat, though.  Make sure that you aren't going to be charged by your current host for the upload. Also, you need enough room on your current physical machine to make a mirror of it.

In my case, I'm thinking about splitting a single physical server into two servers.  One that will remain the physical server and one that will be hosted with EC2.  This would increase costs, of course, but it creates a better logical separation between certain uses of the machine.

My other use case is to test a yum-based OS upgrade since I can't really upgrade any other way - aside from imaging a slightly newer OS on to the box and reconfiguring everything. However, I noticed the following in one of the FAQs:

8.14.

Can I use my own kernel?

Not at present.

I'm not entirely sure what that means given that people have published many AMIs with many different version of Linux which I didn't think would be using the exact same kernel.

Finally, along the cost lines, don't forget about your time.  That has value to you and/or your company.  To summarize the formula, you've got:

One Time Cost:

(20 cents * GBServer) + (current host cost to upload) + (your time to prep upload)  + (your time to convert to S3 store for persistence)

Monthly Costs:

($73 per server) + (15 cents * GBServer) + (20 cents * bandwidthGB)

Sure, most of this is obvious.  The largest unknown, though, would be the time to convert servers over to have data persist outside of the AMI.  This can either be done by having the application directly store to S3, having a backup system run a frequent full backup of the data directories to AMI and restore on boot, or use one of the filesystem drivers to have the data portion of the filesystem be linked directly to S3. (Where S3 is used, any other off-AMI storage could be considered, but I'm assuming the network connection between the AMIs and S3 is very fast and very low latency.)

Posted by Shane on March 6, 2007 8:50 AM | Permalink