Namenode roll edits – online mode
In this recipe, we will take a look at how to roll edits and keep the size of the metadata to a minimum. Over a period of time, the number of edits files grow and also the Namenode keeps old versions of fsimage file. In a large busy cluster, the edits files could be large, with each of about 1 GB.
This will utilize disk space on Namenode and can cause disk issues in the longer run of the cluster. Also, if the Secondary Namenode is not configured or is not working correctly, these edits files will be in large numbers, with each file of approximately 1 million transactions. Due to this, the Namenode start time will increase and Namenode might not even start if the memory is not sufficient to do the checkpoint operation.
Getting ready
For this recipe, make sure that you have completed the recipe on Hadoop cluster setup, Chapter 1, Hadoop Architecture and Deployment, and have at least HDFS running for a few hour with some data on HDFS.
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