HDFS-13283. Percentage based Reserved Space Calculation for DataNode. Contributed by Lukas Majercak.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java

@@ -26,6 +26,7 @@ import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyRackFaultTolerant;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.RamDiskReplicaLruTracker;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.ReservedSpaceCalculator;
 import org.apache.hadoop.http.HttpConfig;
 
 /** 
@@ -647,8 +648,16 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final String  DFS_DATANODE_DNS_INTERFACE_DEFAULT = "default";
   public static final String  DFS_DATANODE_DNS_NAMESERVER_KEY = "dfs.datanode.dns.nameserver";
   public static final String  DFS_DATANODE_DNS_NAMESERVER_DEFAULT = "default";
+  public static final String DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY =
+      "dfs.datanode.du.reserved.calculator";
+  public static final Class<? extends ReservedSpaceCalculator>
+      DFS_DATANODE_DU_RESERVED_CALCULATOR_DEFAULT =
+          ReservedSpaceCalculator.ReservedSpaceCalculatorAbsolute.class;
   public static final String  DFS_DATANODE_DU_RESERVED_KEY = "dfs.datanode.du.reserved";
   public static final long    DFS_DATANODE_DU_RESERVED_DEFAULT = 0;
+  public static final String  DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY =
+      "dfs.datanode.du.reserved.pct";
+  public static final int     DFS_DATANODE_DU_RESERVED_PERCENTAGE_DEFAULT = 0;
   public static final String  DFS_DATANODE_HANDLER_COUNT_KEY = "dfs.datanode.handler.count";
   public static final int     DFS_DATANODE_HANDLER_COUNT_DEFAULT = 10;
   public static final String  DFS_DATANODE_HTTP_ADDRESS_KEY = "dfs.datanode.http.address";

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java

@@ -78,7 +78,6 @@ import org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.RamDiskReplicaTrack
 import org.apache.hadoop.hdfs.server.protocol.DatanodeStorage;
 import org.apache.hadoop.util.CloseableReferenceCount;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
-import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
 import org.apache.hadoop.util.Timer;
 import org.slf4j.Logger;
@@ -121,7 +120,7 @@ public class FsVolumeImpl implements FsVolumeSpi {
 
   private final File currentDir;    // <StorageDirectory>/current
   private final DF usage;
-  private final long reserved;
+  private final ReservedSpaceCalculator reserved;
   private CloseableReferenceCount reference = new CloseableReferenceCount();
 
   // Disk space reserved for blocks (RBW or Re-replicating) open for write.
@@ -143,9 +142,15 @@ public class FsVolumeImpl implements FsVolumeSpi {
    */
   protected ThreadPoolExecutor cacheExecutor;
 
-  FsVolumeImpl(
+  FsVolumeImpl(FsDatasetImpl dataset, String storageID, StorageDirectory sd,
-      FsDatasetImpl dataset, String storageID, StorageDirectory sd,
       FileIoProvider fileIoProvider, Configuration conf) throws IOException {
+    // outside tests, usage created in ReservedSpaceCalculator.Builder
+    this(dataset, storageID, sd, fileIoProvider, conf, null);
+  }
+
+  FsVolumeImpl(FsDatasetImpl dataset, String storageID, StorageDirectory sd,
+      FileIoProvider fileIoProvider, Configuration conf, DF usage)
+      throws IOException {
 
     if (sd.getStorageLocation() == null) {
       throw new IOException("StorageLocation specified for storage directory " +
@@ -157,23 +162,20 @@ public class FsVolumeImpl implements FsVolumeSpi {
     this.storageLocation = sd.getStorageLocation();
     this.currentDir = sd.getCurrentDir();
     this.storageType = storageLocation.getStorageType();
-    this.reserved = conf.getLong(DFSConfigKeys.DFS_DATANODE_DU_RESERVED_KEY
-        + "." + StringUtils.toLowerCase(storageType.toString()), conf.getLong(
-        DFSConfigKeys.DFS_DATANODE_DU_RESERVED_KEY,
-        DFSConfigKeys.DFS_DATANODE_DU_RESERVED_DEFAULT));
     this.configuredCapacity = -1;
+    this.usage = usage;
     if (currentDir != null) {
       File parent = currentDir.getParentFile();
-      this.usage = new DF(parent, conf);
       cacheExecutor = initializeCacheExecutor(parent);
       this.metrics = DataNodeVolumeMetrics.create(conf, parent.getPath());
     } else {
-      this.usage = null;
       cacheExecutor = null;
       this.metrics = null;
     }
     this.conf = conf;
     this.fileIoProvider = fileIoProvider;
+    this.reserved = new ReservedSpaceCalculator.Builder(conf)
+        .setUsage(usage).setStorageType(storageType).build();
   }
 
   protected ThreadPoolExecutor initializeCacheExecutor(File parent) {
@@ -399,7 +401,7 @@ public class FsVolumeImpl implements FsVolumeSpi {
   @VisibleForTesting
   public long getCapacity() {
     if (configuredCapacity < 0) {
-      long remaining = usage.getCapacity() - reserved;
+      long remaining = usage.getCapacity() - getReserved();
       return remaining > 0 ? remaining : 0;
     }
 
@@ -439,8 +441,9 @@ public class FsVolumeImpl implements FsVolumeSpi {
 
   private long getRemainingReserved() throws IOException {
     long actualNonDfsUsed = getActualNonDfsUsed();
-    if (actualNonDfsUsed < reserved) {
+    long actualReserved = getReserved();
-      return reserved - actualNonDfsUsed;
+    if (actualNonDfsUsed < actualReserved) {
+      return actualReserved - actualNonDfsUsed;
     }
     return 0L;
   }
@@ -454,10 +457,11 @@ public class FsVolumeImpl implements FsVolumeSpi {
    */
   public long getNonDfsUsed() throws IOException {
     long actualNonDfsUsed = getActualNonDfsUsed();
-    if (actualNonDfsUsed < reserved) {
+    long actualReserved = getReserved();
+    if (actualNonDfsUsed < actualReserved) {
       return 0L;
     }
-    return actualNonDfsUsed - reserved;
+    return actualNonDfsUsed - actualReserved;
   }
 
   @VisibleForTesting
@@ -476,7 +480,7 @@ public class FsVolumeImpl implements FsVolumeSpi {
   }
 
   long getReserved(){
-    return reserved;
+    return reserved.getReserved();
   }
 
   @VisibleForTesting

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImplBuilder.java

@@ -19,7 +19,9 @@ package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 
 import java.io.IOException;
 
+import com.google.common.annotations.VisibleForTesting;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.DF;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
 import org.apache.hadoop.hdfs.server.datanode.FileIoProvider;
@@ -34,12 +36,14 @@ public class FsVolumeImplBuilder {
   private StorageDirectory sd;
   private Configuration conf;
   private FileIoProvider fileIoProvider;
+  private DF usage;
 
   public FsVolumeImplBuilder() {
     dataset = null;
     storageID = null;
     sd = null;
     conf = null;
+    usage = null;
   }
 
   FsVolumeImplBuilder setDataset(FsDatasetImpl dataset) {
@@ -67,15 +71,25 @@ public class FsVolumeImplBuilder {
     return this;
   }
 
+  @VisibleForTesting
+  FsVolumeImplBuilder setUsage(DF newUsage) {
+    this.usage = newUsage;
+    return this;
+  }
+
   FsVolumeImpl build() throws IOException {
     if (sd.getStorageLocation().getStorageType() == StorageType.PROVIDED) {
       return new ProvidedVolumeImpl(dataset, storageID, sd,
           fileIoProvider != null ? fileIoProvider :
             new FileIoProvider(null, null), conf);
     }
+    if (null == usage) {
+      // set usage unless overridden by unit tests
+      usage = new DF(sd.getCurrentDir().getParentFile(), conf);
+    }
     return new FsVolumeImpl(
         dataset, storageID, sd,
         fileIoProvider != null ? fileIoProvider :
-            new FileIoProvider(null, null), conf);
+            new FileIoProvider(null, null), conf, usage);
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/ProvidedVolumeImpl.java

@@ -270,7 +270,7 @@ class ProvidedVolumeImpl extends FsVolumeImpl {
   ProvidedVolumeImpl(FsDatasetImpl dataset, String storageID,
       StorageDirectory sd, FileIoProvider fileIoProvider,
       Configuration conf) throws IOException {
-    super(dataset, storageID, sd, fileIoProvider, conf);
+    super(dataset, storageID, sd, fileIoProvider, conf, null);
     assert getStorageLocation().getStorageType() == StorageType.PROVIDED:
       "Only provided storages must use ProvidedVolume";
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/ReservedSpaceCalculator.java

@@ -0,0 +1,227 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.DF;
+import org.apache.hadoop.fs.StorageType;
+import org.apache.hadoop.util.StringUtils;
+
+import java.lang.reflect.Constructor;
+
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_PERCENTAGE_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_CALCULATOR_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY;
+
+/**
+ * Used for calculating file system space reserved for non-HDFS data.
+ */
+public abstract class ReservedSpaceCalculator {
+
+  /**
+   * Used for creating instances of ReservedSpaceCalculator.
+   */
+  public static class Builder {
+
+    private final Configuration conf;
+
+    private DF usage;
+    private StorageType storageType;
+
+    public Builder(Configuration conf) {
+      this.conf = conf;
+    }
+
+    public Builder setUsage(DF newUsage) {
+      this.usage = newUsage;
+      return this;
+    }
+
+    public Builder setStorageType(
+        StorageType newStorageType) {
+      this.storageType = newStorageType;
+      return this;
+    }
+
+    ReservedSpaceCalculator build() {
+      try {
+        Class<? extends ReservedSpaceCalculator> clazz = conf.getClass(
+            DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY,
+            DFS_DATANODE_DU_RESERVED_CALCULATOR_DEFAULT,
+            ReservedSpaceCalculator.class);
+
+        Constructor constructor = clazz.getConstructor(
+            Configuration.class, DF.class, StorageType.class);
+
+        return (ReservedSpaceCalculator) constructor.newInstance(
+            conf, usage, storageType);
+      } catch (Exception e) {
+        throw new IllegalStateException(
+            "Error instantiating ReservedSpaceCalculator", e);
+      }
+    }
+  }
+
+  private final DF usage;
+  private final Configuration conf;
+  private final StorageType storageType;
+
+  ReservedSpaceCalculator(Configuration conf, DF usage,
+      StorageType storageType) {
+    this.usage = usage;
+    this.conf = conf;
+    this.storageType = storageType;
+  }
+
+  DF getUsage() {
+    return usage;
+  }
+
+  long getReservedFromConf(String key, long defaultValue) {
+    return conf.getLong(key + "." + StringUtils.toLowerCase(
+        storageType.toString()), conf.getLong(key, defaultValue));
+  }
+
+  /**
+   * Return the capacity of the file system space reserved for non-HDFS.
+   *
+   * @return the number of bytes reserved for non-HDFS.
+   */
+  abstract long getReserved();
+
+
+  /**
+   * Based on absolute number of reserved bytes.
+   */
+  public static class ReservedSpaceCalculatorAbsolute extends
+      ReservedSpaceCalculator {
+
+    private final long reservedBytes;
+
+    public ReservedSpaceCalculatorAbsolute(Configuration conf, DF usage,
+        StorageType storageType) {
+      super(conf, usage, storageType);
+      this.reservedBytes = getReservedFromConf(DFS_DATANODE_DU_RESERVED_KEY,
+          DFS_DATANODE_DU_RESERVED_DEFAULT);
+    }
+
+    @Override
+    long getReserved() {
+      return reservedBytes;
+    }
+  }
+
+  /**
+   * Based on percentage of total capacity in the storage.
+   */
+  public static class ReservedSpaceCalculatorPercentage extends
+      ReservedSpaceCalculator {
+
+    private final long reservedPct;
+
+    public ReservedSpaceCalculatorPercentage(Configuration conf, DF usage,
+        StorageType storageType) {
+      super(conf, usage, storageType);
+      this.reservedPct = getReservedFromConf(
+          DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY,
+          DFS_DATANODE_DU_RESERVED_PERCENTAGE_DEFAULT);
+    }
+
+    @Override
+    long getReserved() {
+      return getPercentage(getUsage().getCapacity(), reservedPct);
+    }
+  }
+
+  /**
+   * Calculates absolute and percentage based reserved space and
+   * picks the one that will yield more reserved space.
+   */
+  public static class ReservedSpaceCalculatorConservative extends
+      ReservedSpaceCalculator {
+
+    private final long reservedBytes;
+    private final long reservedPct;
+
+    public ReservedSpaceCalculatorConservative(Configuration conf, DF usage,
+        StorageType storageType) {
+      super(conf, usage, storageType);
+      this.reservedBytes = getReservedFromConf(DFS_DATANODE_DU_RESERVED_KEY,
+          DFS_DATANODE_DU_RESERVED_DEFAULT);
+      this.reservedPct = getReservedFromConf(
+          DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY,
+          DFS_DATANODE_DU_RESERVED_PERCENTAGE_DEFAULT);
+    }
+
+    long getReservedBytes() {
+      return reservedBytes;
+    }
+
+    long getReservedPct() {
+      return reservedPct;
+    }
+
+    @Override
+    long getReserved() {
+      return Math.max(getReservedBytes(),
+          getPercentage(getUsage().getCapacity(), getReservedPct()));
+    }
+  }
+
+  /**
+   * Calculates absolute and percentage based reserved space and
+   * picks the one that will yield less reserved space.
+   */
+  public static class ReservedSpaceCalculatorAggressive extends
+      ReservedSpaceCalculator {
+
+    private final long reservedBytes;
+    private final long reservedPct;
+
+    public ReservedSpaceCalculatorAggressive(Configuration conf, DF usage,
+        StorageType storageType) {
+      super(conf, usage, storageType);
+      this.reservedBytes = getReservedFromConf(DFS_DATANODE_DU_RESERVED_KEY,
+          DFS_DATANODE_DU_RESERVED_DEFAULT);
+      this.reservedPct = getReservedFromConf(
+          DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY,
+          DFS_DATANODE_DU_RESERVED_PERCENTAGE_DEFAULT);
+    }
+
+    long getReservedBytes() {
+      return reservedBytes;
+    }
+
+    long getReservedPct() {
+      return reservedPct;
+    }
+
+    @Override
+    long getReserved() {
+      return Math.min(getReservedBytes(),
+          getPercentage(getUsage().getCapacity(), getReservedPct()));
+    }
+  }
+
+  private static long getPercentage(long total, long percentage) {
+    return (total * percentage) / 100;
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -326,6 +326,20 @@
   </description>
 </property>
 
+<property>
+  <name>dfs.datanode.du.reserved.calculator</name>
+  <value>org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.ReservedSpaceCalculator$ReservedSpaceCalculatorAbsolute</value>
+  <description>Determines the class of ReservedSpaceCalculator to be used for
+    calculating disk space reservedfor non-HDFS data. The default calculator is
+    ReservedSpaceCalculatorAbsolute which will use dfs.datanode.du.reserved
+    for a static reserved number of bytes. ReservedSpaceCalculatorPercentage
+    will use dfs.datanode.du.reserved.pct to calculate the reserved number
+    of bytes based on the size of the storage. ReservedSpaceCalculatorConservative and
+    ReservedSpaceCalculatorAggressive will use their combination, Conservative will use
+    maximum, Aggressive minimum. For more details see ReservedSpaceCalculator.
+  </description>
+</property>
+
 <property>
   <name>dfs.datanode.du.reserved</name>
   <value>0</value>
@@ -338,6 +352,20 @@
   </description>
 </property>
 
+<property>
+  <name>dfs.datanode.du.reserved.pct</name>
+  <value>0</value>
+  <description>Reserved space in percentage. Read dfs.datanode.du.reserved.calculator to see
+    when this takes effect. The actual number of bytes reserved will be calculated by using the
+    total capacity of the data directory in question. Specific storage type based reservation
+    is also supported. The property can be followed with corresponding storage types
+    ([ssd]/[disk]/[archive]/[ram_disk]) for cluster with heterogeneous storage.
+    For example, reserved percentage space for RAM_DISK storage can be configured using property
+    'dfs.datanode.du.reserved.pct.ram_disk'. If specific storage type reservation is not configured
+    then dfs.datanode.du.reserved.pct will be used.
+  </description>
+</property>
+
 <property>
   <name>dfs.namenode.name.dir</name>
   <value>file://${hadoop.tmp.dir}/dfs/name</value>

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestFsVolumeList.java

@@ -19,6 +19,7 @@ package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 
 import com.google.common.base.Supplier;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.DF;
 import org.apache.hadoop.fs.FileSystemTestHelper;
 import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
@@ -40,15 +41,18 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.TimeoutException;
+
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.fail;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class TestFsVolumeList {
 
-  private final Configuration conf = new Configuration();
+  private Configuration conf;
   private VolumeChoosingPolicy<FsVolumeImpl> blockChooser =
       new RoundRobinVolumeChoosingPolicy<>();
   private FsDatasetImpl dataset = null;
@@ -63,6 +67,7 @@ public class TestFsVolumeList {
     blockScannerConf.setInt(DFSConfigKeys.
         DFS_DATANODE_SCAN_PERIOD_HOURS_KEY, -1);
     blockScanner = new BlockScanner(null, blockScannerConf);
+    conf = new Configuration();
   }
 
   @Test(timeout=30000)
@@ -227,4 +232,87 @@ public class TestFsVolumeList {
         actualNonDfsUsage - duReserved;
     assertEquals(expectedNonDfsUsage, spyVolume.getNonDfsUsed());
   }
+
+  @Test
+  public void testDfsReservedPercentageForDifferentStorageTypes()
+      throws IOException {
+    conf.setClass(DFSConfigKeys.DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY,
+        ReservedSpaceCalculator.ReservedSpaceCalculatorPercentage.class,
+        ReservedSpaceCalculator.class);
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY, 15);
+
+    File volDir = new File(baseDir, "volume-0");
+    volDir.mkdirs();
+
+    DF usage = mock(DF.class);
+    when(usage.getCapacity()).thenReturn(4000L);
+    when(usage.getAvailable()).thenReturn(1000L);
+
+    // when storage type reserved is not configured, should consider
+    // dfs.datanode.du.reserved.pct
+    FsVolumeImpl volume = new FsVolumeImplBuilder()
+        .setConf(conf)
+        .setDataset(dataset)
+        .setStorageID("storage-id")
+        .setStorageDirectory(
+            new StorageDirectory(StorageLocation.parse(
+                "[RAM_DISK]" + volDir.getPath())))
+        .setUsage(usage)
+        .build();
+
+    assertEquals(600, volume.getReserved());
+    assertEquals(3400, volume.getCapacity());
+    assertEquals(400, volume.getAvailable());
+
+    // when storage type reserved is configured.
+    conf.setLong(
+        DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY + "."
+            + StringUtils.toLowerCase(StorageType.RAM_DISK.toString()), 10);
+    conf.setLong(
+        DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY + "."
+            + StringUtils.toLowerCase(StorageType.SSD.toString()), 50);
+    FsVolumeImpl volume1 = new FsVolumeImplBuilder()
+        .setConf(conf)
+        .setDataset(dataset)
+        .setStorageID("storage-id")
+        .setStorageDirectory(
+            new StorageDirectory(StorageLocation.parse(
+                "[RAM_DISK]" + volDir.getPath())))
+        .setUsage(usage)
+        .build();
+    assertEquals(400, volume1.getReserved());
+    assertEquals(3600, volume1.getCapacity());
+    assertEquals(600, volume1.getAvailable());
+    FsVolumeImpl volume2 = new FsVolumeImplBuilder()
+        .setConf(conf)
+        .setDataset(dataset)
+        .setStorageID("storage-id")
+        .setStorageDirectory(
+            new StorageDirectory(StorageLocation.parse(
+                "[SSD]" + volDir.getPath())))
+        .setUsage(usage)
+        .build();
+    assertEquals(2000, volume2.getReserved());
+    assertEquals(2000, volume2.getCapacity());
+    assertEquals(0, volume2.getAvailable());
+    FsVolumeImpl volume3 = new FsVolumeImplBuilder()
+        .setConf(conf)
+        .setDataset(dataset)
+        .setStorageID("storage-id")
+        .setStorageDirectory(
+            new StorageDirectory(StorageLocation.parse(
+                "[DISK]" + volDir.getPath())))
+        .setUsage(usage)
+        .build();
+    assertEquals(600, volume3.getReserved());
+    FsVolumeImpl volume4 = new FsVolumeImplBuilder()
+        .setConf(conf)
+        .setDataset(dataset)
+        .setStorageID("storage-id")
+        .setStorageDirectory(
+            new StorageDirectory(StorageLocation.parse(volDir.getPath())))
+        .setUsage(usage)
+        .build();
+    assertEquals(600, volume4.getReserved());
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestReservedSpaceCalculator.java

@@ -0,0 +1,171 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.DF;
+import org.apache.hadoop.fs.StorageType;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY;
+import static org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.ReservedSpaceCalculator.ReservedSpaceCalculatorAbsolute;
+import static org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.ReservedSpaceCalculator.ReservedSpaceCalculatorAggressive;
+import static org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.ReservedSpaceCalculator.ReservedSpaceCalculatorConservative;
+import static org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.ReservedSpaceCalculator.ReservedSpaceCalculatorPercentage;
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.when;
+
+/**
+ * Unit testing for different types of ReservedSpace calculators.
+ */
+public class TestReservedSpaceCalculator {
+
+  private Configuration conf;
+  private DF usage;
+  private ReservedSpaceCalculator reserved;
+
+  @Before
+  public void setUp() {
+    conf = new Configuration();
+    usage = Mockito.mock(DF.class);
+  }
+
+  @Test
+  public void testReservedSpaceAbsolute() {
+    conf.setClass(DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY,
+        ReservedSpaceCalculatorAbsolute.class,
+        ReservedSpaceCalculator.class);
+
+    // Test both using global configuration
+    conf.setLong(DFS_DATANODE_DU_RESERVED_KEY, 900);
+
+    checkReserved(StorageType.DISK, 10000, 900);
+    checkReserved(StorageType.SSD, 10000, 900);
+    checkReserved(StorageType.ARCHIVE, 10000, 900);
+  }
+
+  @Test
+  public void testReservedSpaceAbsolutePerStorageType() {
+    conf.setClass(DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY,
+        ReservedSpaceCalculatorAbsolute.class,
+        ReservedSpaceCalculator.class);
+
+    // Test DISK
+    conf.setLong(DFS_DATANODE_DU_RESERVED_KEY + ".disk", 500);
+    checkReserved(StorageType.DISK, 2300, 500);
+
+    // Test SSD
+    conf.setLong(DFS_DATANODE_DU_RESERVED_KEY + ".ssd", 750);
+    checkReserved(StorageType.SSD, 1550, 750);
+  }
+
+  @Test
+  public void testReservedSpacePercentage() {
+    conf.setClass(DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY,
+        ReservedSpaceCalculatorPercentage.class,
+        ReservedSpaceCalculator.class);
+
+    // Test both using global configuration
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY, 10);
+    checkReserved(StorageType.DISK, 10000, 1000);
+    checkReserved(StorageType.SSD, 10000, 1000);
+    checkReserved(StorageType.ARCHIVE, 10000, 1000);
+
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY, 50);
+    checkReserved(StorageType.DISK, 4000, 2000);
+    checkReserved(StorageType.SSD, 4000, 2000);
+    checkReserved(StorageType.ARCHIVE, 4000, 2000);
+  }
+
+  @Test
+  public void testReservedSpacePercentagePerStorageType() {
+    conf.setClass(DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY,
+        ReservedSpaceCalculatorPercentage.class,
+        ReservedSpaceCalculator.class);
+
+    // Test DISK
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY + ".disk", 20);
+    checkReserved(StorageType.DISK, 1600, 320);
+
+    // Test SSD
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY + ".ssd", 50);
+    checkReserved(StorageType.SSD, 8001, 4000);
+  }
+
+  @Test
+  public void testReservedSpaceConservativePerStorageType() {
+    // This policy should take the maximum of the two
+    conf.setClass(DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY,
+        ReservedSpaceCalculatorConservative.class,
+        ReservedSpaceCalculator.class);
+
+    // Test DISK + taking the reserved bytes over percentage,
+    // as that gives more reserved space
+    conf.setLong(DFS_DATANODE_DU_RESERVED_KEY + ".disk", 800);
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY + ".disk", 20);
+    checkReserved(StorageType.DISK, 1600, 800);
+
+    // Test ARCHIVE + taking reserved space based on the percentage,
+    // as that gives more reserved space
+    conf.setLong(DFS_DATANODE_DU_RESERVED_KEY + ".archive", 1300);
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY + ".archive", 50);
+    checkReserved(StorageType.ARCHIVE, 6200, 3100);
+  }
+
+  @Test
+  public void testReservedSpaceAggresivePerStorageType() {
+    // This policy should take the maximum of the two
+    conf.setClass(DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY,
+        ReservedSpaceCalculatorAggressive.class,
+        ReservedSpaceCalculator.class);
+
+    // Test RAM_DISK + taking the reserved bytes over percentage,
+    // as that gives less reserved space
+    conf.setLong(DFS_DATANODE_DU_RESERVED_KEY + ".ram_disk", 100);
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY + ".ram_disk", 10);
+    checkReserved(StorageType.RAM_DISK, 1600, 100);
+
+    // Test ARCHIVE + taking reserved space based on the percentage,
+    // as that gives less reserved space
+    conf.setLong(DFS_DATANODE_DU_RESERVED_KEY + ".archive", 20000);
+    conf.setLong(DFS_DATANODE_DU_RESERVED_PERCENTAGE_KEY + ".archive", 5);
+    checkReserved(StorageType.ARCHIVE, 100000, 5000);
+  }
+
+  @Test(expected = IllegalStateException.class)
+  public void testInvalidCalculator() {
+    conf.set(DFS_DATANODE_DU_RESERVED_CALCULATOR_KEY, "INVALIDTYPE");
+    reserved = new ReservedSpaceCalculator.Builder(conf)
+        .setUsage(usage)
+        .setStorageType(StorageType.DISK)
+        .build();
+  }
+
+  private void checkReserved(StorageType storageType,
+      long totalCapacity, long reservedExpected) {
+    when(usage.getCapacity()).thenReturn(totalCapacity);
+
+    reserved = new ReservedSpaceCalculator.Builder(conf).setUsage(usage)
+        .setStorageType(storageType).build();
+    assertEquals(reservedExpected, reserved.getReserved());
+  }
+}