The contents of a RAM disk are copied to an image file in nonvolatile memory on power-down and copied back on reboot to provide an appearance of persistence. A locking method can use in-use tables to limit access to the same blocks of data in a RAM disk....http://www.google.com.hk/patents/US7631139?utm_source=gb-gplus-share專利 US7631139 - System and method for persistent RAM disk
