How can you overwrite the replication factors in HDFS?

Question

I am writing temp files to HDFS with replication=1, so I expect the blocks to be stored on the writing node. Are there any tips, in general, for optimizing write performance to HDFS? I use 128K buffers in the write() calls. Are there any parameters that can be set on the connection or in HDFS configuration to optimize this use pattern?

Answer 1

The replication factor in HDFS can be modified or overwritten in 2 ways-

1)Using the Hadoop FS Shell, replication factor can be changed per file basis using the below command-

$hadoop fs –setrep –w 2 /my/test_file (test_file is the filename whose replication factor will be set to 2)

2)Using the Hadoop FS Shell, replication factor of all files under a given directory can be modified using the below command-

3)$hadoop fs –setrep –w 5 /my/test_dir (test_dir is the name of the directory and all the files in this directory will have a replication factor set to 5)