High Availability
A single NameNode is a single point of failure in Hadoop. Hadoop 2.x introduced NameNode High Availability (HA) using two NameNodes — an Active and a Standby — to eliminate this risk.
Security & Kerberos
By default, Hadoop runs in simple authentication mode, which offers no real security — any user can impersonate any other. For production clusters, Apache Hadoop supports Kerberos for strong mutual authentication.
HDFS Federation
The Single NameNode Bottleneck
HDFS Snapshots
What Are Snapshots?
Hadoop Configuration Tuning
Default Hadoop settings are conservative and designed for small test clusters. Production clusters require careful tuning across HDFS, MapReduce, and YARN to achieve good throughput and stability.
Rack Awareness
What Is Rack Awareness?