vSAN performs block-level deduplication and compression to save storage space. This allows you to make more efficient and cost-effective use of storage in your VMware Cloud on AWS SDDC.
Deduplication removes redundant data blocks. Compression removes additional redundant data within each data block. These techniques work together or separately to reduce the amount of physical storage required to store the data. VMware vSAN applies deduplication followed by compression as it moves data from the cache tier to the capacity tier.
Deduplication and compression are automatically enabled for VMware Cloud on AWS clusters containing i3 hosts and cannot be turned off. Clusters containing i3en hosts are automatically enabled for compression only. Enabling compression without deduplication improves performance. It also allows for increased availability, because the fault domain can be restricted to a single disk rather than a disk group.
Deduplication occurs inline when data is written back from the cache tier to the capacity tier. The deduplication algorithm uses a fixed block size and is applied within each disk group. Redundant copies of a block within the same disk group are deduplicated.
Storage savings resulting from deduplication and compression are highly dependent on the workload data. On average, storage space savings are in the range of 1.5X to 2X.