Comment 2 for bug 1201503

Upon more investigation, the definition of this varies a bit by provider.

- For openstack, you can create custom flavors that have a default root disk size upon booting. The cloud image will resize the root filesystem to match the available root disk size.
- For ec2 ebs instances, which we default to using, the root disk size defaults to 8G but you can specify a custom root disk size via block device mapping. refs:
 - http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/block-device-mapping-concepts.html
 - http://alestic.com/2009/12/ec2-ebs-boot-resize

Example:

  ec2-run-instances --key KEYPAIR --block-device-mapping /dev/sda1=:100 AMI

... creates an instance that boots with a created on-demand 100G ebs which gets thrown away when the instance is terminated. We'll need to implement passing the block device mapping in the goamz run instance api call to expose this.

- For azure, the os disk size is hardcoded and might make less sense to specify a constraint on disk size, but we should do it for consistency anyway. refs: http://msdn.microsoft.com/en-us/library/windowsazure/dn197896.aspx