diff --git a/Cache/MappedBlockCache.cpp b/Cache/MappedBlockCache.cpp
index d8a8da4..103f846 100644
--- a/Cache/MappedBlockCache.cpp
+++ b/Cache/MappedBlockCache.cpp
@@ -8,7 +8,6 @@
 
 #include <Cache/MappedBlockCache.h>
 #include <ProFUSE/Exception.h>
-#include <ProFUSE/auto.h>
 
 
 
@@ -48,18 +47,51 @@ void MappedBlockCache::unload(unsigned block, int flags)
 #undef __METHOD__
 #define __METHOD__ "MappedBlockCache::unload"
 
+    // kBlockCommitNow implies kBlockDirty. 
     if (flags & kBlockCommitNow)
     {
-        _dirty = true;
-        sync();
+        sync(block)
         return;
     }
 
     if (flags & kBlockDirty) _dirty = true;
 }
 
+// sync everything.
 void MappedBlockCache::sync()
 {
   _device->sync();
   _dirty = false;
 }
+
+/*
+ *
+ * sync an individual page.
+ *
+ */
+void MappedBlockCache::sync(unsigned block)
+{
+#undef __METHOD__
+#define __METHOD__ "MappedBlockCache::sync"
+
+
+    int pageSize = ::getpagesize();
+        
+    void *start = (_data + block * 512) % pagesize;
+    void *end = (_data + 512 + block * 512) % pagesize;
+
+    if (::msync(start, pagesize, MS_SYNC) != 0)
+        throw POSIXException(__METHOD__ ": msync", errno);
+    
+    if (start != end)
+    {
+        if (::msync(end, pagesize, MS_SYNC) != 0)
+            throw POSIXException(__METHOD__ ": msync", errno);    
+    }
+}
+
+void MappedBlockCache::markDirty(unsigned block)
+{
+    _dirty = true;
+}
+
diff --git a/Cache/MappedBlockCache.h b/Cache/MappedBlockCache.h
index 319a584..c10a362 100644
--- a/Cache/MappedBlockCache.h
+++ b/Cache/MappedBlockCache.h
@@ -1,7 +1,7 @@
 #ifndef __MAPPED_BLOCK_CACHE_H__
 #define __MAPPED_BLOCK_CACHE_H__
 
-#include <BlockCache.h>
+#include <Cache/BlockCache.h>
 
 namespace Device {
 
@@ -11,7 +11,7 @@ class MappedBlockCache : public BlockCache {
     MappedBlockCache(BlockDevice *, void *data);
     virtual ~MappedBlockCache();
 
-    virtual void sync() = 0;
+    virtual void sync();
     virtual void write(unsigned block, const void *vp);
 
 
@@ -20,7 +20,9 @@ class MappedBlockCache : public BlockCache {
     virtual void markDirty(unsigned block);
 
     private:
-        void *_data;
+        void sync(block);
+        
+        uint8_t *_data;
         bool _dirty;
 
 };