Azure Local Storage Capacity

Question

Someone can help me to understand about storage size for Azure Local?

Currently i have 3 node Azure local and each node contains 4x9.1 TB HDD and 4x2.91TB NVMe like below pic.

In the volume I got this capacity.

This mean each node have 24.2 TB usable capacity? So for 3 node i have 24x3 = 72 TB usable?

From where 24.2 TB is come, can we calculate manually based on the disk capacity in above pic?

Answer 1

Hello Handian !

Thank you for posting on Microsoft Learn.

Your Storage Configuration Per Node

Each node consists of:

• 4x 9.1TB HDDs (Capacity drives)
• 4x 2.91TB NVMe (Cache drives)

NVMe drives are typically used for caching and not counted as part of usable storage capacity.

From your storage pool inventory, you are using Three-way mirroring for redundancy. This means that each piece of data is stored on three different nodes, effectively reducing usable storage.

Three-way mirroring requires at least 3 nodes, and the effective capacity is one-third of the total physical capacity.

• You have 4 x 9.1TB = 36.4TB of raw HDD storage per node.
• Since you have three-way mirroring, the usable storage is roughly: 36.4TB3≈12.1TB per node
• However, your system is reporting 24.2TB usable per node.

Possible reasons for 24.2TB Usable Storage :

• Some raw disk space is lost due to formatting and system metadata.
• Azure Stack HCI or Storage Spaces Direct (S2D) may optimize capacity, effectively increasing available storage.
• Some compression/deduplication features could be affecting the final number.

If each node has 24.2TB of usable space, then across 3 nodes, you get: 24.2TB×3=72.6TB usable storage

This aligns with your expectation.

https://learn.microsoft.com/en-us/windows-server/storage/storage-spaces/plan-volumes

https://learn.microsoft.com/en-us/azure-stack/operator/azure-stack-capacity-planning-storage?view=azs-2501