Cache Size

This screen controls SD read cache size and IO scheduler. You can select the sd card at the top, should the device have multiple SD cards available. If you cannot find your SD card, please send a "support request" from app settings mentioning the problem. On supported kernels you can also control "fsync", more about it here. 

WARNING: It is not recommended to disable fsync when kernel/ROM/device is unstable as the risk of data loss increases if device reboots unexpectedly. 

Tap on boot (in action bar) button to have current settings applied on boot. Any changes applied since boot will be lost on next boot otherwise.