Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/SegmentWriter.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/SegmentWriter.java	(date 1441109076000)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/SegmentWriter.java	(date 1441124689000)
@@ -224,10 +224,7 @@
             }
 
             SegmentId id = segment.getSegmentId();
-            log.debug("Writing data segment {} ({} bytes)", id, length);
-            store.writeSegment(id, buffer, buffer.length - length, length);
 
-            // Keep this segment in memory as it's likely to be accessed soon
             ByteBuffer data;
             if (buffer.length - length > 4096) {
                 data = ByteBuffer.allocate(length);
@@ -236,6 +233,11 @@
             } else {
                 data = ByteBuffer.wrap(buffer, buffer.length - length, length);
             }
+
+            log.debug("Writing data segment {} ({} bytes)", id, length);
+            store.writeSegment(id, data.array(), data.position(), length);
+
+            // Keep this segment in memory as it's likely to be accessed soon
             tracker.setSegment(id, new Segment(tracker, id, data));
 
             buffer = createNewBuffer(version);
Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/file/FileStore.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/file/FileStore.java	(date 1441109076000)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/file/FileStore.java	(date 1441124689000)
@@ -56,7 +56,6 @@
 
 import com.google.common.base.Stopwatch;
 import com.google.common.collect.Maps;
-
 import org.apache.jackrabbit.oak.api.Blob;
 import org.apache.jackrabbit.oak.plugins.blob.BlobStoreBlob;
 import org.apache.jackrabbit.oak.plugins.segment.CompactionMap;
@@ -960,6 +959,11 @@
             }
         }
 
+        Segment segment = cache.get(new UUID(msb, lsb));
+        if (segment != null) {
+            return segment;
+        }
+
         if (writer != null) {
             synchronized (this) {
                 try {
@@ -996,6 +1000,8 @@
         throw new SegmentNotFoundException(id);
     }
 
+    final Map<UUID, Segment> cache = Maps.newConcurrentMap();
+
     @Override
     public synchronized void writeSegment(
             SegmentId id, byte[] data, int offset, int length) {
@@ -1004,6 +1010,8 @@
                     id.getMostSignificantBits(),
                     id.getLeastSignificantBits(),
                     data, offset, length);
+            ByteBuffer bb = ByteBuffer.wrap(data, offset, length);
+            cache.put(id.asUUID(), new Segment(id.getTracker(), id, bb));
             if (size >= maxFileSize) {
                 newWriter();
             }
@@ -1015,6 +1023,7 @@
     private void newWriter() throws IOException {
         if (writer.isDirty()) {
             writer.close();
+            cache.clear();
 
             List<TarReader> list =
                     newArrayListWithCapacity(1 + readers.size());