Safe to Enable Deduplication on Mirror Composed of Dynamic Disks in Windows Server 2025?

Hello Dale, I am Henry and I want to share my insights regarding your concern.

While technically possible, enabling Data Deduplication on a mirrored volume composed of Dynamic Disks is not recommended and is considered unsafe from a supportability standpoint.

1. Dynamic Disks are a legacy feature. Microsoft is not testing new features like modern Data Deduplication against them. This creates a high risk of unexpected behavior, data corruption, or recovery issues.
   • Unsupported Configuration: You will likely not receive support from Microsoft if you encounter issues with this specific combination.
   • Recovery Complexity: If a disk fails, recovering a deduplicated volume on a broken dynamic mirror is significantly more complex and failure-prone than with modern solutions.
2. If you're unfamiliar with the context of Storage Spaces, I recommend looking into it as part of your research.
   • Convert the disks back to Basic Disks.
   • Create a Storage Pool using the two physical disks.
   • From the pool, create a Virtual Disk (Storage Space) with Two-way mirror resiliency.
   • Format the resulting volume and then enable Data Deduplication on it.

I hope this information is helpful.