diff --git a/core/src/main/scala/org/apache/spark/shuffle/unsafe/UnsafeShuffleManager.scala b/core/src/main/scala/org/apache/spark/shuffle/unsafe/UnsafeShuffleManager.scala
index 04ac811ac7966..fe092683d5400 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/unsafe/UnsafeShuffleManager.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/unsafe/UnsafeShuffleManager.scala
@@ -17,7 +17,6 @@
 
 package org.apache.spark.shuffle.unsafe
 
-import java.io.{FileOutputStream, OutputStream}
 import java.nio.ByteBuffer
 import java.util
 
@@ -29,7 +28,7 @@ import org.apache.spark.scheduler.MapStatus
 import org.apache.spark.serializer.Serializer
 import org.apache.spark.shuffle._
 import org.apache.spark.shuffle.sort.SortShuffleManager
-import org.apache.spark.storage.ShuffleBlockId
+import org.apache.spark.storage.{BlockObjectWriter, ShuffleBlockId}
 import org.apache.spark.unsafe.PlatformDependent
 import org.apache.spark.unsafe.memory.{MemoryBlock, TaskMemoryManager}
 import org.apache.spark.unsafe.sort.UnsafeSorter
@@ -104,7 +103,14 @@ private[spark] class UnsafeShuffleWriter[K, V](
 
   private[this] val blockManager = SparkEnv.get.blockManager
 
-  private def sortRecords(records: Iterator[_ <: Product2[K, V]]): java.util.Iterator[KeyPointerAndPrefix] = {
+  // Use getSizeAsKb (not bytes) to maintain backwards compatibility of on units are provided
+  private[this] val fileBufferSize =
+    SparkEnv.get.conf.getSizeAsKb("spark.shuffle.file.buffer", "32k").toInt * 1024
+
+  private[this] val serializer = Serializer.getSerializer(dep.serializer).newInstance()
+
+  private def sortRecords(
+      records: Iterator[_ <: Product2[K, V]]): java.util.Iterator[KeyPointerAndPrefix] = {
     val sorter = new UnsafeSorter(
       context.taskMemoryManager(),
       DummyRecordComparator,
@@ -112,7 +118,6 @@ private[spark] class UnsafeShuffleWriter[K, V](
       PartitionerPrefixComparator,
       4096  // initial size
     )
-    val serializer = Serializer.getSerializer(dep.serializer).newInstance()
     val PAGE_SIZE = 1024 * 1024 * 1
 
     var currentPage: MemoryBlock = null
@@ -178,32 +183,31 @@ private[spark] class UnsafeShuffleWriter[K, V](
     sorter.getSortedIterator
   }
 
-  private def writeSortedRecordsToFile(sortedRecords: java.util.Iterator[KeyPointerAndPrefix]): Array[Long] = {
+  private def writeSortedRecordsToFile(
+      sortedRecords: java.util.Iterator[KeyPointerAndPrefix]): Array[Long] = {
     val outputFile = shuffleBlockManager.getDataFile(dep.shuffleId, mapId)
     val blockId = ShuffleBlockId(dep.shuffleId, mapId, IndexShuffleBlockManager.NOOP_REDUCE_ID)
     val partitionLengths = new Array[Long](partitioner.numPartitions)
 
     var currentPartition = -1
-    var prevPartitionLength: Long = 0
-    var out: OutputStream = null
+    var writer: BlockObjectWriter = null
 
     // TODO: don't close and re-open file handles so often; this could be inefficient
 
     def closePartition(): Unit = {
-      out.flush()
-      out.close()
-      partitionLengths(currentPartition) = outputFile.length() - prevPartitionLength
+      writer.commitAndClose()
+      partitionLengths(currentPartition) = writer.fileSegment().length
     }
 
     def switchToPartition(newPartition: Int): Unit = {
-      assert (newPartition > currentPartition, s"new partition $newPartition should be >= $currentPartition")
+      assert (newPartition > currentPartition,
+        s"new partition $newPartition should be >= $currentPartition")
       if (currentPartition != -1) {
         closePartition()
-        prevPartitionLength = partitionLengths(currentPartition)
       }
-      println(s"Before switching to partition $newPartition, partition lengths are " + partitionLengths.toSeq)
       currentPartition = newPartition
-      out = blockManager.wrapForCompression(blockId, new FileOutputStream(outputFile, true))
+      writer =
+        blockManager.getDiskWriter(blockId, outputFile, serializer, fileBufferSize, writeMetrics)
     }
 
     while (sortedRecords.hasNext) {
@@ -214,18 +218,24 @@ private[spark] class UnsafeShuffleWriter[K, V](
       }
       val baseObject = memoryManager.getPage(keyPointerAndPrefix.recordPointer)
       val baseOffset = memoryManager.getOffsetInPage(keyPointerAndPrefix.recordPointer)
-      val recordLength = PlatformDependent.UNSAFE.getLong(baseObject, baseOffset + 8)
+      val recordLength: Int = PlatformDependent.UNSAFE.getLong(baseObject, baseOffset + 8).toInt
       println("Base offset is " + baseOffset)
       println("Record length is " + recordLength)
       // TODO: need to have a way to figure out whether a serializer supports relocation of
       // serialized objects or not.  Sandy also ran into this in his patch (see
       // https://github.com/apache/spark/pull/4450).  If we're using Java serialization, we might
       // as well just bypass this optimized code path in favor of the old one.
-      var i: Int = 0
-      while (i < recordLength) {
-        out.write(PlatformDependent.UNSAFE.getByte(baseObject, baseOffset + 16 + i))
-        i += 1
-      }
+      // TODO: re-use a buffer or avoid double-buffering entirely
+      val arr: Array[Byte] = new Array[Byte](recordLength)
+      PlatformDependent.copyMemory(
+        baseObject,
+        baseOffset + 16,
+        arr,
+        PlatformDependent.BYTE_ARRAY_OFFSET,
+        recordLength)
+      writer.write(arr)
+      // TODO: add a test that detects whether we leave this call out:
+      writer.recordWritten()
     }
     closePartition()