001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package org.apache.hadoop.hdfs;
020    
021    import java.util.Arrays;
022    import java.util.ArrayList;
023    import java.util.List;
024    
025    import org.apache.hadoop.classification.InterfaceAudience;
026    import org.apache.hadoop.classification.InterfaceStability;
027    
028    /**
029     * Defines the types of supported storage media. The default storage
030     * medium is assumed to be DISK.
031     */
032    @InterfaceAudience.Public
033    @InterfaceStability.Unstable
034    public enum StorageType {
035      DISK(false),
036      SSD(false),
037      ARCHIVE(false),
038      RAM_DISK(true);
039    
040      private final boolean isTransient;
041    
042      public static final StorageType DEFAULT = DISK;
043    
044      public static final StorageType[] EMPTY_ARRAY = {};
045    
046      private static final StorageType[] VALUES = values();
047    
048      StorageType(boolean isTransient) { this.isTransient = isTransient; }
049    
050      public boolean isTransient() {
051        return isTransient;
052      }
053    
054      public boolean isMovable() {
055        return !isTransient;
056      }
057    
058      public static List<StorageType> asList() {
059        return Arrays.asList(VALUES);
060      }
061    
062      public static List<StorageType> getMovableTypes() {
063        List<StorageType> movableTypes = new ArrayList<StorageType>();
064        for (StorageType t : VALUES) {
065          if ( t.isTransient == false ) {
066            movableTypes.add(t);
067          }
068        }
069        return movableTypes;
070      }
071    }