diff --git a/Cache/BlockCache.h b/Cache/BlockCache.h
index ce629e4..f740c32 100644
--- a/Cache/BlockCache.h
+++ b/Cache/BlockCache.h
@@ -4,12 +4,19 @@
 #include <stdint.h>
 #include <vector>
 
+class MappedFile;
+class Device::BlockDevice;
+
 namespace Device {
 
-class BlockDevice;
-class MappedFile;
 
 
+enum {
+    kBlockDirty = 1,
+    kBlockCommitNow = 2,
+    kBlockReuse = 3
+} BlockReleaseFlags;
+
 class BlockCache {
 public:
 
@@ -27,10 +34,11 @@ public:
     virtual void read(unsigned block, void *bp);
 
     virtual void *acquire(unsigned block) = 0;
-    virtual void release(unsigned block, bool dirty) = 0;
+    virtual void release(unsigned block, int flags) = 0 ;
     virtual void markDirty(unsigned block) = 0;
     
-    void release(unsigned block) { release(block, false); }
+    void release(unsigned block) { release(block, 0); }
+    void release(unsigned block, bool dirty)  { release(block, dirty ? kBlockDirty : 0); }
 
 protected:
     BlockCache(BlockDevice *device);
@@ -52,7 +60,7 @@ public:
 
 
     virtual void *acquire(unsigned block);
-    virtual void release(unsigned block, bool dirty);
+    virtual void release(unsigned block, int flags);
     virtual void markDirty(unsigned block);
 
 
@@ -96,25 +104,6 @@ private:
     decrementCount(Entry *);
 };
 
-class MappedBlockCache : public BlockCache {
-    public:
-    
-    MappedBlockCache(BlockDevice *, void *data);
-    virtual ~MappedBlockCache();
-    
-    virtual void sync() = 0;
-    virtual void write(unsigned block, const void *vp);
-
-
-    virtual void *acquire(unsigned block);
-    virtual void release(unsigned block, bool dirty);
-    virtual void markDirty(unsigned block);
-    
-    private:
-        void *_data;
-    
-};
-
 } // namespace
 
-#endif
\ No newline at end of file
+#endif
diff --git a/Cache/ConcreteBlockCache.h b/Cache/ConcreteBlockCache.h
new file mode 100644
index 0000000..2a97969
--- /dev/null
+++ b/Cache/ConcreteBlockCache.h
@@ -0,0 +1,64 @@
+#ifndef __CONCRETE_BLOCK_CACHE_H__
+#define __CONCRETE_BLOCK_CACHE_H__
+
+#include <vector>
+
+#include <BlockCache.h>
+
+namespace Device {
+
+class ConcreteBlockCache : public BlockCache {
+public:
+    ConcreteBlockCache(BlockDevice *device, unsigned size = 16);
+    virtual ~ConcreteBlockCache();
+
+    virtual void sync();
+    virtual void write(unsigned block, const void *vp) = 0;
+
+
+    virtual void *acquire(unsigned block);
+    virtual void release(unsigned block, int flags);
+    virtual void markDirty(unsigned block);
+
+
+private:
+    struct Entry {
+        unsigned block;
+        unsigned count;
+        bool dirty;
+
+        struct Entry *next;
+        struct Entry *prev;
+        struct Entry *nextHash;
+
+        uint8_t buffer[512];
+
+    };
+
+    enum { HashTableSize = 23 };
+
+    std::vector<Entry *>_buffers;
+
+    Entry *_hashTable[HashTableSize];
+
+    Entry *_first;
+    Entry *_last;
+
+
+    unsigned hashFunction(unsigned block);
+
+    Entry *findEntry(unsigned block);
+    void removeEntry(unsigned block);
+    void addEntry(Entry *);
+
+    Entry *newEntry(unsigned block);
+
+    void pushEntry(Entry *);
+
+    void setLast(Entry *);
+
+    incrementCount(Entry *);
+    decrementCount(Entry *);
+};
+
+}
diff --git a/Cache/MappedBlockCache.cpp b/Cache/MappedBlockCache.cpp
new file mode 100644
index 0000000..d8a8da4
--- /dev/null
+++ b/Cache/MappedBlockCache.cpp
@@ -0,0 +1,65 @@
+
+#include <algorithm>
+#include <cerrno>
+
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <Cache/MappedBlockCache.h>
+#include <ProFUSE/Exception.h>
+#include <ProFUSE/auto.h>
+
+
+
+using namespace Device;
+
+using ProFUSE::Exception;
+using ProFUSE::POSIXException;
+
+
+MappedBlockCache::MappedBlockCache(Device *device, void *data) :
+    BlockCache(device)
+{
+    _data = (uint8_t *)data;
+    _dirty = false;
+}
+
+MappedBlockCache::~MappedBlockCache()
+{
+  if (_dirty) sync();
+}
+
+
+void *MappedBlockCache::acquire(unsigned block)
+{
+#undef __METHOD__
+#define __METHOD__ "MappedBlockCache::load"
+    
+    if (block >= blocks())
+        throw Exception(__METHOD__ ": Invalid block.");
+        
+    
+    return _data + block * 512;
+}
+
+void MappedBlockCache::unload(unsigned block, int flags)
+{
+#undef __METHOD__
+#define __METHOD__ "MappedBlockCache::unload"
+
+    if (flags & kBlockCommitNow)
+    {
+        _dirty = true;
+        sync();
+        return;
+    }
+
+    if (flags & kBlockDirty) _dirty = true;
+}
+
+void MappedBlockCache::sync()
+{
+  _device->sync();
+  _dirty = false;
+}
diff --git a/Cache/MappedBlockCache.h b/Cache/MappedBlockCache.h
new file mode 100644
index 0000000..319a584
--- /dev/null
+++ b/Cache/MappedBlockCache.h
@@ -0,0 +1,30 @@
+#ifndef __MAPPED_BLOCK_CACHE_H__
+#define __MAPPED_BLOCK_CACHE_H__
+
+#include <BlockCache.h>
+
+namespace Device {
+
+class MappedBlockCache : public BlockCache {
+    public:
+
+    MappedBlockCache(BlockDevice *, void *data);
+    virtual ~MappedBlockCache();
+
+    virtual void sync() = 0;
+    virtual void write(unsigned block, const void *vp);
+
+
+    virtual void *acquire(unsigned block);
+    virtual void release(unsigned block, int flags);
+    virtual void markDirty(unsigned block);
+
+    private:
+        void *_data;
+        bool _dirty;
+
+};
+
+} // namespace
+
+