6 Nodes: To utilize the Fault Set feature (which provides higher availability than standard SDS grouping, typically for rack awareness), PowerFlex requires a minimum configuration.

The Math:

A Protection Domain requires a minimum of 3 Fault Sets to support the 2-copy mirroring (Primary, Secondary, and a third location for rebuilding if a set fails).

Dell PowerFlex engineering requirements state that each Fault Set must contain at least 2 SDS nodes to ensure local redundancy and performance balance within the set.

$3 text{ Fault Sets} times 2 text{ Nodes} = 6 text{ Nodes}$ minimum.