A common hack to improve the performance of MySQL and other programs is to configure their tmp space to be a ram based file system. However in the case of MySQL if you fill up the space the query in question, and sometimes the server, will crash. How would I go about "extending" the ramfs mount/filesystem such that when it is full it will continue to disk. I realize writing to disk is a performance hit, but in this case the performance hit is less important than a stability hit. The key point is that the Ramfs device would have the priority for all writes on a space available basis.