Walter Su created HDFS-9122:
-------------------------------
Summary: DN automatically add more volumes to avoid large volume
Key: HDFS-9122
URL: https://issues.apache.org/jira/browse/HDFS-9122
Project: Hadoop HDFS
Issue Type: Improvement
Reporter: Walter Su
Currently if a DataNode has too many blocks, it partition blockReport by
storage. In practice, we've seen a single storage can contains large amount of
blocks and the report even exceeds the max RPC data length. Storage density
increases quickly, a DataNode can hold more and more blocks. It's harder to
include so many blocks in one RPC report. One option is "Support splitting
BlockReport of a storage into multiple RPC"(HDFS-9011).
I'm thinking maybe we could add more "logical" volumes (more storage
directories in one device). DataNodeStorageInfo in NameNode is cheap. And
Processing a single blockReport need NN hold the lock, so splitting one big
volume to many volume can avoid a single processing hold lock too long.
We can support wildcard in dfs.datanode.data.dir. Like
/physical-volume/dfs/data/dir*
When a volume exceeds threshold(like 1m blocks), DN automatically create a new
storage directory, also a volume. We have to change
RoundRobinVolumeChoosingPolicy as well, once we chosen a physical volume, we
choose the logical volume which has least number of blocks.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
