Understanding Recommendation Strategies and Cost Estimates

A migration plan in Oracle Cloud Migrations aims at evaluating the migration costs based on migration strategies and provide recommendation strategies that might meet the expected migration performance.

The migration recommendation strategies can be configured based on several strategies that you define when creating or editing a migration plan. These strategies are:

Resource type

The resources to which a strategy can be applied are the CPU, memory, or both.

Strategy type

The strategy type is based on the following options:

  • Based on VM configuration: The strategy type based on this option is As is, which means to copy the existing VM configuration as is. The configurations are for CPU and RAM.
  • Based on metrics: The strategy types based on this option are:
    • Average: Uses average values of the resources that are used.
    • Percentile: Uses a selected percentile such as P50, P90, P95, and P99. The strategy type is based on the percentile of usage of the selected resource.
    • Peak: Uses peak usage values during the selected period. You can consider the peak strategy type as the highest observed CPU usage such as P100.

By default, the same strategy type is used for CPU and memory calculation. However, you can use different strategy types for resources such as, As is for memory, and Percentile P95 for CPU.

Adjustment multiplier

To match the performance of source VMs with target VMs, an adjustment multiplier index can be applied to any strategy types.

For example, if the CPUs on OCI compute are 25% more powerful than CPUs on the source VM, you can consider that using an adjustment index lesser than 1 is the key factor. In this case, the formula used to calculate the adjustment multiplier is, 1 /1.25 = 0.8.

By default, if the target configuration recommends 10 CPUs, the adjustment multiplier can be decreased to 8 as each of the CPU is 25% more powerful.

To properly utilize this strategy, we recommend that you use a CPU benchmark that best represents the production load. Perform the following steps:
  1. Collect benchmark scores on both on-premises and OCI by using an equal number of CPUs in both the source and target VMs.
  2. Calculate adjustment multiplier based on the formula, <score in VMware>/<score in OCI>.
  3. Verify the adjustment multiplier result and if it is closer to 1, then don't change the default values.

If the benchmark score is higher on the OCI environment compared to the on-premises environment, the adjustment multiplier is less than 1 and vice versa.

Metric type

The following are the two types of metrics collected from the source VMs and you can configure these metrics during asset discovery.
  • Historical metrics: This is collected automatically.
  • Monitoring or Runtime metrics: The monitoring metrics are precise compared to historical metrics and uses the OCI monitoring service. If the usage of monitoring metrics exceeds the capacity of the free usage, you need to incur extra costs.

    The percentile strategy type is not available with the historical metrics. Therefore, if you choose a percentile strategy, you can only view the runtime metrics.

Metric time window

The metric time window is the monitoring period that you can use to calculate the average, percentile, or peak usage of resources.

Shape type

The shape type is a mechanism to limit recommendations for a specific family of shapes. For example, if you want to use only Intel CPUs even if AMD is available at a lower cost, you can define this configuration to limit recommendations only to Intel shape types.

Estimated Cost for Each Month

The cost estimates are based on the configuration of recommendation strategies and the target assets.

To evaluate the cost of running the migration assets in OCI, Oracle Cloud Migrations considers the cost of the recommended compute shapes and sizes of the volumes that are used by VM. No other costs are included.

The cost of resources is requested for your tenancy and is based on the actual subscription rate of the tenancy. However, note that Oracle Cloud Migrations provides only an estimated cost and it might not exactly reflect the actual cost.

The cost of the temporary resources used during the migration (block volumes, hydration server instances, monitoring metrics, and so on) is not included in the estimated cost for each month.