The Hitachi Content Platform (HCP) cluster maintains operational integrity and prevents "split-brain" scenarios through a quorum mechanism. This mechanism requires a simple majority of the nodes in the cluster to be online and communicating. The formula to determine the minimum number of nodes for a quorum is (total number of nodes / 2) + 1. If the number of active nodes falls below this threshold, the cluster will cease most operations to protect data consistency until a quorum is re-established. This ensures that only one partition of a potentially fractured cluster can be active at any given time.

A. A minimum of exactly 50% of the nodes is insufficient, as it does not create a majority and could lead to a tie in a network partition, risking a split-brain condition.

B. A quorum LUN is a concept used in storage array clustering (like Hitachi Global-Active Device) or hypervisor clusters, not for the internal software-based quorum of an HCP system.

C. A Command Device is a specific logical unit used for out-of-band management of Hitachi Virtual Storage Platform (VSP) arrays and is not relevant to the HCP software's node-based quorum.

1. Hitachi Content Platform (HCP) v9.3 System Administration Guide (MK-93HCP003-11), Section: "About the HCP system," Subsection: "Nodes." The documentation states, "To ensure data consistency, an HCP system requires a majority of the nodes in the system to be running. This majority is called a quorum. If fewer than a quorum of the nodes are running, the HCP system stops running." This directly supports the principle of a majority, which is mathematically represented as (N/2) + 1.

2. Hitachi Content Platform (HCP) v9.2 Core-v Concepts and Features (HC-F1HCP001-08), Chapter 2: "HCP Architecture," Section: "Cluster Quorum." This section explains that HCP uses a majority-based quorum to function. It details that if a cluster loses enough nodes to lose quorum, the remaining nodes will enter a read-only or unavailable state to prevent inconsistent writes. This confirms the requirement for more than 50% of nodes to be active.