TR-3749:
DEDUPLICATION CONSIDERATIONS WITH VMFS AND RDM LUNS
Enabling deduplication when provisioning LUNs produces storage savings. However, the default behavior
of a LUN is to reserve an amount of storage equal to the provisioned LUN. This design means that
although the storage array reduces the amount of capacity consumed, any gains made with deduplication
are for the most part unrecognizable, because the space reserved for LUNs is not reduced.
To recognize the storage savings of deduplication with LUNs, you must enable NetApp LUN thin
provisioning.
Note: Although deduplication reduces the amount of consumed storage, the VMware administrative
team does not see this benefit directly, because its view of the storage is at a LUN layer, and
LUNs always represent their provisioned capacity, whether they are traditional or thin
provisioned. The NetApp Virtual Storage Console (VSC) provides the VI administrator with the
storage use at all layers in the storage stack.
When you enable dedupe on thin-provisioned LUNs, NetApp recommends deploying these LUNs in
FlexVol volumes that are also thin provisioned with a capacity that is 2x the size of the LUN. When the
LUN is deployed in this manner, the FlexVol volume acts merely as a quota. The storage consumed by
the LUN is reported in FlexVol and its containing aggregate.