Configuring BlockCache
You can configure BlockCache in two different ways in HBase: the default on-heap LruBlockCache and the BucketCache, which is usually off-heap.
If you have less than 20 GB of RAM available for use by HBase, consider tailoring the default on-heap BlockCache implementation (LruBlockCache) for your cluster.
If you have more than 20 GB of RAM available, consider adding off-heap BlockCache (BucketCache).