content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.client.file.cache.store;
  
  /**
   * This represents the different page store implementations that can be instantiated.
   */
  public enum PageStoreType {
    /**
     * A simple store with pages on the local filesystem.
     */
    LOCAL(PageStoreType.LOCAL_OVERHEAD_RATIO),
    /**
     * A store that utilizes RocksDB to store and retrieve pages.
     */
    ROCKS(PageStoreType.ROCKS_OVERHEAD_RATIO),
    /**
     * A simple store with pages on the memory (HeapByteBuffer).
     */
    MEM(PageStoreType.MEMORY_OVERHEAD_RATIO);
  
    // We assume there will be some overhead using ByteBuffer as a page store,
    // i.e., with 1GB space allocated, we
    // expect no more than 1024MB / (1 + BUFF_MEMORY_OVERHEAD_RATIO) logical data stored
    private static final double MEMORY_OVERHEAD_RATIO = 0.1;
    // We assume 20% overhead using Rocksdb as a page store, i.e., with 1GB space allocated, we
    // expect no more than 1024MB/(1+20%)=853MB logical data stored
    private static final double ROCKS_OVERHEAD_RATIO = 0.2;
    // We assume there will be some overhead using local fs as a page store,
    // i.e., with 1GB space allocated, we
    // expect no more than 1024MB / (1 + LOCAL_OVERHEAD_RATIO) logical data stored
    private static final double LOCAL_OVERHEAD_RATIO = 0.05;
    private final double mOverheadRatio;
  
    /**
     * @param overheadRatio
     */
    PageStoreType(double overheadRatio) {
      mOverheadRatio = overheadRatio;
    }
  
    /**
     * @return overhead ratio
     */
    public double getOverheadRatio() {
      return mOverheadRatio;
    }
  }
  