Define Deduplication and Compression
vSAN can perform block-level deduplication and compression to save storage space. When you enable deduplication and compression on a vSAN all-flash cluster, redundant data within each disk group is reduced. let me simplify this in simple words, deduplication removes redundant data blocks, whereas compression removes additional redundant data within each data block. These techniques work together to reduce the amount of space required to store the data
Let's have a more understanding through below snap
When you enable or disable deduplication and compression, vSAN performs a rolling reformat of every disk group on every host. Depending on the data stored on the vSAN datastore, this process might take a long time. Do not perform these operations frequently. If you plan to disable deduplication and compression, you must first verify that enough physical capacity is available to place your data
VSAN Scenario
When deduplication and compression are enabled on the vSAN cluster, it might take several minutes for capacity updates to be reflected in the Capacity monitor as disk space is reclaimed and reallocated.
Important Note :
# Compression-only vSAN is applied on a per-disk basis.
# Deduplication and compression might not be effective for encrypted VMs, because VM Encryption encrypts data on the host before it is written out to storage. Consider storage tradeoffs when using VM Encryption.
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