The document summarizes how the HDFS Namenode is a single point of failure by design and discusses Facebook's solution called AvatarNode to address this. It notes that the Namenode is responsible for all metadata operations and was originally prioritized for features and performance over reliability. It then provides details on HDFS usage at Facebook, including that 41% of data warehouse incidents and 10% of messaging incidents are related to the Namenode SPOF. AvatarNode is presented as Facebook's open source solution to introduce Namenode high availability, though it has limitations compared to future automated solutions being worked on in HDFS.