private ByteBuffAllocator getByteBuffAllocator() {
      if (data instanceof HFileBlock) {
        return ((HFileBlock) data).getByteBuffAllocator();
      }
      return ByteBuffAllocator.HEAP;
    }
Block Entry stored in the memory with key,data and so on
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/BucketCache.java