In a Huawei FusionInsight HD cluster, the standard recommendation for deploying Flume server nodes (often acting as aggregators) is two. This configuration establishes a high-availability (HA) setup, typically in an active/standby or load-balanced pair. Deploying two nodes ensures service continuity by preventing a single point of failure (SPOF). If one node fails, the other can take over the data collection and aggregation tasks, which is a critical requirement for production environments to avoid data loss and service interruption.

A. Deploying a single node creates a single point of failure, which is not a recommended practice for any critical service in a production cluster.

C. While deploying three nodes can provide higher availability, it is generally not the standard baseline recommendation for Flume and adds unnecessary resource overhead and complexity.

D. Four nodes would be a deployment for very large-scale, high-throughput requirements and is not the standard recommendation for a typical HA configuration.

1. Huawei FusionInsight HD 6.5.1 Product Documentation - Planning Guide, Chapter: "Planning Services and Roles". This guide details the deployment principles for FusionInsight components. For services requiring high availability, it specifies deploying instances on at least two different nodes to ensure redundancy and failover capabilities. The Flume service, when configured for aggregation, falls under this HA requirement.

2. Huawei FusionInsight HD Administrator Guide, Section: "Component High Availability (HA) Architecture". This section describes the HA mechanisms for the platform. It explains that critical services are deployed in pairs (active/standby) on different nodes to guarantee service availability, a principle that applies to the Flume aggregation tier.