Updating your mobile device to Android Kitkat 4.4 is not recommended due to the new External SD Card Write Restriction imposed by Google, the developers of the Android Operating System. Applications, and users via an app, are stripped of the ability to write any kind of data on the external SD card, limiting write access to internal storage only.
If the Android device is rooted (jail-broke) then the restriction can be bypassed. However, not all devices can be root exploited, and not all users wish to risk invalidating their warranty by doing so.
references
- http://blog.b1.org/sandbox-an-easier-work-with-sd-card-in-kitkat/
- https://play.google.com/store/apps/details?id=com.geeksoft.extcardpatch&hl=en
- How can I get Android KitKat to work with my SD cards?