What is the primary purpose of a Protection Domain in PowerFlex?

The Protection Domain (PD) is the fundamental unit of fault isolation.

Isolating storage resources for fault containment (Option B): The PowerFlex mesh-mirroring algorithm works only within a Protection Domain. Data on Node A (in PD1) will only be mirrored to other nodes inside PD1. It will never be mirrored to PD2.

Why is this important? If a catastrophic software bug or a massive power surge affects one Protection Domain, the damage is contained there. The other Protection Domains continue to function normally. It allows administrators to segment the cluster (e.g., PD_Production vs. PD_Test) to ensure that issues in one environment do not bleed into another.