The current major release, Hadoop 2.0 offers several significant HDFS improvements including new append-pipeline, federation, wire compatibility, NameNode HA, Snapshots, and performance improvements. We describe how to take advantages of these new features and their benefits. We cover some architectural improvements in detail such as HA, Federation and Snapshots. The second half of the talk describes the current features that are under development for the next HDFS release. This includes much needed data management features such as backup and Disaster Recovery. We add support for different classes of storage devices such as SSDs and open interfaces such as NFS; together these extend HDFS as a more general storage system. Hadoop has recently been extended to run first-class on Windows which expands its enterprise reach and allows integration with the rich tool-set available on Windows. As with every release we will continue improvements to performance, diagnosability and manageability of HDFS. To conclude, we discuss the reliability, the state of HDFS adoption, and some of the misconceptions and myths about HDFS.
8. 8
Managing Namespaces
• Federation has multiple namespaces
• Don’t you need a single global namespace?
– Some tenants want private namespace
• Hadoop as service – each tenant its own namespace
– Global? Key is to share the data and the names used
to access the data
• A single global namespace is one way share
• Client-side mount table is another way to share.
– Shared mount-table => “global” shared view
– Personalized mount-table => per-application view
• Share the data that matter by mounting it
• Client-side implementation of mount tables
– No single point of failure
– No hotspot for root and top level directories
Client-side
mount-table
homeproject
NS1 NS3NS2
NS4
tmp
/
data
O'Reilly Strata & Hadoop8
21. 21
Next Steps… first class support for volumes
• NameServer - Container for
namespaces
› Lots of small namespace volumes
• Chosen per user/tenant/data feed
• Management policies (quota, …)
• Mount tables for unified namespace
• Can be managed by a central volume
server
› Move namespace for balancing
• WorkingSet of namespace in memory
› Many more namespaces in a server
• Number of NameServers =
› Sum of (Namespace working set)
› Sum of (Namespace throughput)
2
Datanode Datanode…
…
NameServers as
Containers of Namespaces
Storage Layer
O'Reilly Strata & Hadoop