How-To Calculate Cinder's Provisioned Ratio

Problem

You want to calculate the provisioned ratio for a Cinder Host in terms of the scheduler's capacity_filter. Helpful in scenarios where Cinder Pool is exceeding the max_over_subscription_ratio.

The ratio of provisioned capacity over total capacity 1.01 has exceeded the maximum over subscription ratio 1.00 on host UUID@Backend#IP:/cinder.

Environment

• Platform9 Managed OpenStack - All versions
• Cinder

Answer

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provisioned_ratio = ((backend_state.provisioned_capacity_gb + requested_size) / total)

For example:

1. Consider a Cinder Host to have allocated_capacity_gb of 6740 GB and total_capacity_gb equal to 6881.28 GB. This information can be retrieved using the following command.

# cinder get-pools --detail| allocated_capacity_gb | 6740| max_over_subscription_ratio | 1.0| total_capacity_gb | 6881.28

2. Let us consider a volume to be provisioned/migrated to be of size 200 GB.
3. The provisioned ratio calculated is to be 1.01 which higher than the subscription ratio of 1.0.

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provisioned ratio = ((  6740 + 200 ) / 6881.28 ) = 1.01