When you own a reserved instance in a linked or payer account, AWS applies a reserved instance pricing to running instance in one of your linked accounts. If the RI is owned in a linked account that has that instance type running, it will be applied within the account. However, if the RI is owned in an account that does not have the appropriate instance type, AWS will apply the RI randomly to a linked account that contains that RI type.
Orbitera gives you a few options for handling reserved instances in your bill that allows you to maximize your margin.
Option 1 - use "Pass RI Optimization to Customer"
In the edit customer screen there is an option called "Pass RI Optimization to Customer." You can think of this like a hammer - it will force Orbitera to ignore which account an RI was purchased in, and simply pass any RI pricing that is in the consolidated bill without changing the pricing. You should use this setting if you cannot provide Orbitera with read-only access to a linked account that has purchased RIs. The downside is that if an RI that was purchased elsewhere is applied to this customer's accounts, Orbitera will not be able to substitute the RI price with the on-demand price, potentially reducing margins.
Option 2 - set a third party read-only role for each linked account that purchases RIs
Orbitera uses read-only access to determine which account actually purchased a reserved instance. If these roles are set for all linked accounts that purchase RIs, Orbitera can ensure that only those accounts that purchased RIs are given the reduced RI rates.
These roles can be set either by editing the account as it appears for a customer, or by editing an account in the cloud accounts table.
If you have additional questions on how Orbitera accurately calculates RI charges please contact us directly.