How to calculate the block storage usage in Openstack
Problem
How to calculate the block storage usage, free/total capacity, and oversubscription ratio using OpenStack Cinder metrics.
This article explains how to calculate the block storage usage from cinder get-pools --detail in OpenStack. It is applicable for any Cinder backend (e.g., Ceph, HPE 3PAR, NetApp, etc.) and helps you interpret key metrics related to block storage usage, provisioning, and backend status.
Environment
Platform9 Managed OpenStack - v4.0 and Higher
Cinder
Key Terms
Term | Description |
|---|---|
Total Capacity | Physical capacity of the backend storage. |
Allocated Capacity | Actual space used on the backend storage (physical usage). |
Free Capacity | Unused portion of physical storage. |
Provisioned Capacity | Total logical volume size requested by users. May exceed physical space if thin provisioning is used. |
Oversubscription Ratio | How much logical capacity is provisioned relative to what's physically used. |
Max Oversubscription Ratio | Configured upper limit of how much Cinder is allowed to oversubscribe the backend. |
Answer
Source admin.rc file.
Run below command to list all the available cinder pools.
Example output for Cinder with Ceph as backend storage.
Calculations
Allocated Capacity (Physical Usage)
Provisioned Capacity (Logical Usage)
Oversubscription Ratio (Actual)
Free and Total Capacity
If all the cinder pools use same backend storage pool.
- If cinder pools use different backend storage pools.
Maximum Provisioned Capacity Allowed
