Review manpage about memory size

TODO

@@ -5,6 +5,25 @@ This is the list of TODO items for SnapRAID.
 
 - Minor
 
+* Check how to reduce memory occupation using smaller memory block.
+We can theoreticallty reduce the memory occupation from 28/36 to
+17 bytes. 16 for the hash and 1 for the type.
+We can store the parity_position<->file,pos relation using some form of binary tree,
+and then drop completely blockarr, and the extra data in memory_block.
+A simpler simplification is to convert, blockarr to a parity_position->file,pos
+relation, removing the file pointer inside the block.
+
+struct node {
+	uint32 parity_pos /* parity position */
+	file* file; /* pointer at the file */
+	uint32 offset; /* position in the file */
+	uint32 count; /* number of sequential blocks */
+	void* left_by_pp; /* tree by parity_pos */
+	void* right_by_pp;
+	void* left_by_fp; /* tree by file,offset */
+	void* right_by_fp;
+};
+
 * Restore ownership and permissions, at least in Unix.
 
 * Restore directory timestamps.