Apache Spark is well-suited for real-time data processing in the Hadoop ecosystem. It offers in-memory processing and supports iterative algorithms, making it faster than traditional batch processing with MapReduce. Spark is particularly advantageous for applications requiring low-latency data analysis.

In Hadoop's MapReduce, the Shuffle phase occurs between the Map and Reduce phases. During this phase, the output from the Map phase is shuffled and sorted before being sent to the Reduce tasks for further processing.

In situations where data consistency is critical, the Incremental Import functionality of Sqoop should be emphasized. It allows for the extraction of only the new or updated data since the last import, ensuring consistency between Hadoop and the RDBMS.

The feature in Apache Flume that allows for the dynamic addition of new data sources during runtime is 'Source Interceptors.' These interceptors can be configured to modify, filter, or enrich events as they enter the Flume pipeline, facilitating the seamless integration of new data sources without interrupting the data flow.

High Availability (HA) in Hadoop ensures continued cluster operation in the event of the primary NameNode failure. With HA, a standby NameNode takes over seamlessly, preventing downtime and data loss.

When migrating large datasets to Hadoop, considerations for data integrity and efficiency should include ensuring data consistency and validation. It involves verifying that data is accurately transferred, maintaining its integrity during the migration process.

Hive uses Predicate Pushdown to optimize query performance by pushing the filtering conditions closer to the data source, reducing the amount of data scanned during a query and improving overall efficiency.

The primary tool used for monitoring Hadoop cluster performance is Hadoop ResourceManager. It provides information about the resource utilization, job execution, and overall health of the cluster. Administrators use ResourceManager to ensure efficient resource allocation and identify any performance bottlenecks.

When dealing with time-series data in Hadoop, the optimal combination for performance is using the Parquet file format with Snappy compression. Parquet is columnar storage, and Snappy provides fast compression, making it efficient for analytical queries on time-series data.

For optimal results in aggregating data from multiple sources with Hadoop Streaming API, the approach should involve using Combiners for Intermediate Aggregation. Combiners help reduce the amount of data transferred between mappers and reducers, improving overall performance in the aggregation process.