Show disk module only if mounted?

[rieje]

I have a disk module for the path /data which is where a media drive is mounted to. When it gets unmounted, the module shows the same info as my other disk module for /home/user (my system disk).

Is there a way to only show the disk module if the filesystem is mounted by the media disk?

Also was curious what is used to check disk size--I currently have interval set to 30 seconds but it would be nice to get close to real time--would like to know if this is relatively inexpensive to do. From what I understand, there's no event for determining disk size so polling is expensive, right?