HDFS Configuration
The following table describes the default Hadoop Distributed File System (HDFS) parameters
and their settings. You can change these values using the hdfs-site configuration classification. For more information, see Configuring Applications.
Setting dfs.replication to 1 for clusters with fewer than four nodes can lead to HDFS data loss if a single node goes down.
| Parameter | Definition | Default value |
|---|---|---|
| dfs.block.size | The size of HDFS blocks. When operating on data stored in HDFS,
the split size is generally the size of an HDFS block. Larger
numbers provide less task granularity, but also put less strain on
the cluster NameNode.
|
134217728 (128 MB) |
| dfs.replication | The number of copies of each block to store for durability. For
small clusters, set this to 2 because the cluster is small and easy
to restart in case of data loss. You can change the setting to 1, 2,
or 3 as your needs dictate. Amazon EMR automatically calculates the
replication factor based on cluster size. To overwrite the default
value, use the hdfs-site classification.
|
1 for clusters < four nodes 2 for clusters < ten nodes 3 for all other clusters |
