Configuring HBase 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).
In the default configuration, HBase uses a single on-heap cache. If you configure the
BucketCache, the on-heap cache is used for Bloom filters and
indexes, and the off-heap
BucketCache is used to cache data blocks. This is
called the Combined Blockcache configuration. The Combined
allows you to use a larger in-memory cache while reducing the negative impact of garbage
collection in the heap, because HBase manages the
BucketCache instead of
relying on the garbage collector.