Configuring the Storage Policy for the Write-Ahead Log (WAL)

You can configure the preferred HDFS storage policy for HBase's write-ahead log (WAL) replicas. This feature allows you to tune HBase's use of SSDs to your available resources and the demands of your workload.

These instructions assume that you have followed the instructions to configure storage directories for DataNodes, and that your cluster has SSD storage available to HBase. If HDFS is not configured to use SSDs, these configuration changes will have no effect on HBase. The following policies are available:
  • NONE: no preference about where the replicas are written.
  • ONE_SSD: place one replica on SSD storage and the remaining replicas in default storage. This allows you to derive some benefit from SSD storage even if it is a scarce resource in your cluster.
  • ALL_SSD: place all replicas on SSD storage.