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    package org.apache.hadoop.hdfs.server.datanode.fsdataset;
019    
020    import java.io.File;
021    import java.io.IOException;
022    
023    import org.apache.hadoop.hdfs.StorageType;
024    
025    /**
026     * This is an interface for the underlying volume.
027     */
028    public interface FsVolumeSpi {
029      /** @return the StorageUuid of the volume */
030      public String getStorageID();
031    
032      /** @return a list of block pools. */
033      public String[] getBlockPoolList();
034    
035      /** @return the available storage space in bytes. */
036      public long getAvailable() throws IOException;
037    
038      /** @return the base path to the volume */
039      public String getBasePath();
040    
041      /** @return the path to the volume */
042      public String getPath(String bpid) throws IOException;
043    
044      /** @return the directory for the finalized blocks in the block pool. */
045      public File getFinalizedDir(String bpid) throws IOException;
046      
047      public StorageType getStorageType();
048    
049      /**
050       * Reserve disk space for an RBW block so a writer does not run out of
051       * space before the block is full.
052       */
053      public void reserveSpaceForRbw(long bytesToReserve);
054    
055      /**
056       * Release disk space previously reserved for RBW block.
057       */
058      public void releaseReservedSpace(long bytesToRelease);
059    
060      /** Returns true if the volume is NOT backed by persistent storage. */
061      public boolean isTransientStorage();
062    }