Effective costs for cloud VMs
Turbonomic considers a variety of factors when calculating effective monthly cost for a cloud VM.
Effective cost takes into account the on-demand cost and the amortized costs for the associated Reserved Instances and Compute Savings Plans.
Currently, Turbonomic does not calculate effective costs for cloud VMs in AWS GovCloud.
Cost calculation: AWS VMs covered by Compute Savings Plans
For AWS VMs covered by Compute Savings Plans, the calculation for effective cost can be expressed as follows where each discount type is computed separately:
On-demand hourly cost:
(1 - combined coverage percentage) * uptime hours * (on-demand rate)
Effective hourly cost:
-
Savings Plan (SP) hourly cost:
SP coverage percentage * (SP rate)
-
Reserved instance (RI) hourly cost:
RI coverage percentage * (RI rate)
-
On-demand hourly cost:
(1- combined coverage percentage) * (on-demand rate)
Effective monthly cost: (onDemandCost + spCoveredCost + riCoveredCost) * uptime
hours
Where:
-
Combined coverage percentage (Discount Coverage) is the total discount coverage which includes savings plan coverage and reserved instance coverage.
-
The calculation can be expressed as follows:
SP coverage percentage + RI coverage percentage
-
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Uptime is a percentage value that indicates how long a VM has been running since it was first discovered by Turbonomic. For VMs discovered more than 30 days ago, Turbonomic only calculates uptime over the last 30 days.
To estimate monthly on-demand costs, Turbonomic projects the current uptime value into the future. It assumes that future uptime will be similar to the current uptime.
Uptime hours is the same as
uptime percentage * 730
. -
On-demand rate is the hourly on-demand cost for a VM's instance type. This rate includes all license costs, but not storage or IP. For more information about on-demand rates, see this AWS page.
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730 is the number of hours per month that Turbonomic uses to estimate monthly costs.
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SP coverage percentage is the percentage of hourly VM usage that is covered by a savings plan.
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RI coverage percentage is the percentage of hourly VM usage that is covered by a reserved instance.
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SP rate is the discounted hourly cost for a VM covered by a compute savings plan, based on offering rates. Custom rates are not considered.
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RI rate is the discounted hourly cost for a VM covered by a reserved instance, based on offering rates. Custom rates are not considered.
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onDemandCost is the total cost of the VM's hourly usage charged at the on-demand rate.
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spCoveredCost is the total cost of the VM's savings plan covered hourly usage charged at the savings plan rate.
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riCoveredCost is the total cost of the VM's reserved instance covered hourly usage charged at the reserved instance rate.
Cost calculation example: AWS VMs covered by Compute Savings Plans
Assume the following data for a pending scale action for an AWS VM covered by Compute Savings Plans:

The following image shows the calculation populated in the Discount Coverage
tooltip.

Item | Current values | Values after action execution |
---|---|---|
On-demand Rate | $0.364/hr | $0.211/hr |
Savings Plans Rate | $0.215/hr | $0.141/hr |
Reserved Instances Rate | $0.00/hr | $0.00/h |
Discount Coverage | 100% | 100% |
SP coverage | 100% | 100% |
RI coverage | 0% | 0% |
Uptime |
88.7% (.887) |
Turbonomic calculates the following values:
-
On-demand hourly cost:
(1- 1) * 0.364 = $0
- Savings Plan (SP) hourly cost
(1 * 0.215) = $0.215
- Reserved instance (RI) hourly cost
(0 * 0) = $0
- Effective cost before executing the
action:
(0 + 0.215 + 0) * (730 * 0.887) = $139.2
-
Effective cost after executing the action:
(0 + 0.141 + 0) * (730 * 0.887) = $91.2
Turbonomic rounds the calculated values that it displays in the user interface so the results of the calculation may not match the values in the Action Details page.
Since the effective cost is projected to decrease from $139.2/month to $91.2/month, Turbonomic treats the action as a cost-saving measure and shows estimated savings of $48/month.