Current HDFS Namenode stores all of its metadata in RAM. This has allowed Hadoop clusters to scale to 100K concurrent tasks. However, the memory limits the total number of files that a single NameNode can store. While Federation allows one to create multiple volumes with additional Namenodes, there is a need to scale a single namespace and also to store multiple namespaces in a single Namenode.
This talk describes a project that removes the space limits while maintaining similar performance by caching only the working set or hot metadata in Namenode memory. We believe this approach will be very effective because the subset of files that is frequently accessed is much smaller than the full set of files stored in HDFS.
In this talk we will describe our overall approach and give details of our implementation along with some early performance numbers.
Speaker: Lin Xiao, PhD student at Carnegie Mellon University, intern at Hortonworks