To which storage types does Windows Server 2019 data deduplication apply?

Data deduplication in Windows Server 2019 is a feature designed to reduce the amount of storage space used by removing duplicate copies of data. This feature is specifically applicable to non-boot NTFS and ReFS (Resilient File System) volumes.

Using data deduplication on non-boot NTFS and ReFS volumes allows for optimizations that target data storage efficiency. The technology works by identifying redundant data segments and storing only one copy of that data while keeping pointers to the location of the duplicates. This results in significant space savings, especially in environments where large amounts of similar data are stored, such as backups or virtual machine files.

The reason the other options do not qualify is that data deduplication cannot be implemented on system or boot volumes. This limitation exists because these volumes are critical for the system operation and require full access to their data without the added complexity or potential overhead that deduplication could introduce. Therefore, the application of this feature is restricted to non-boot NTFS and ReFS volumes where storage optimization can occur without impacting system stability or performance.