Dynamically resizable disk I/O buffering

Ardour 2.X used a single configuration parameter to determine how much audio was buffered ("cached") from disk during playback. You could change this parameter only by editing your ~/.ardour2/ardour.rc file in a text editor.

Ardour 3.0 has a dynamically controlled buffer size for disk I/O:

disk buffering controls

This means that if you are working on a machine or situation where the default amount of buffering is not enough (or simply doesn't make you comfortable enough), you can simply slide the fader to get more. Alternatively, if you want to use less memory for this and have locates be a bit snappier, you can slide the fader to reduce the amount of buffering. No need to restart the DAW to use different buffer settings!