updated graphics on feature page

docs/features.rst

@@ -254,6 +254,30 @@ which lets peers verify every block of data received from peers, immediately. Th
 gives a minimum turnaround time and completely removes the problem of identifying malicious
 peers.
 
+.. image:: storage.png
+	:align: right
+
+customizable file storage
+-------------------------
+
+libtorrent's storage implementation is customizable. That means a special purpose bittorrent
+client can replace the default way to store files on disk.
+
+When implementing a bittorrent cache, it doesn't matter how the data is stored on disk, as
+long as it can be retrieved and seeded. In that case a new storage class can be implemented
+(inheriting from the ``storage_interface`` class) that avoids the unnecessary step of mapping
+slots to files and offsets. The storage can ignore the file boundaries and just store the
+entire torrent in a single file (which will end up being all the files concatenated). The main
+advantage of this, other than a slight cpu performance gain, is that all file operations would
+be page (and sector) aligned. This enables efficient unbuffered I/O, and can potentially
+lead to more efficient read caching (using the built in disk cache rather than relying on the
+operating system's disk cache).
+
+The storage interface supports operating systems where you can ask for sparse regions
+(such as Windows and Solaris). The advantage of this is that when checking files, the regions
+that are known to be sparse can be skipped, which can reduce the time to check a torrent
+significantly.
+
 
 portability
 ===========