For me, the lack of write ability was first evident when I could read my Titanium Backup folder on the SD card, but no matter what I did I could not write to it nor delete it using things like ES File Explorer.
KitKat doesn’t allow your apps to write to the SD card. It was designed this way to prevent rogue apps from having access to things other apps might store in known locations, such as a rogue app that replaces all of your photos with pictures of David Hasslehoff. Just another level of sandboxing.
Unfortunately, what this means is that without installing a custom ROM with SD-write restrictions disabled, you’re not using your SD card for much other than a few select apps that have rights to it.
NextApp SDFix allows you to modify one file that prevents writing to external storage. It requires root access to run, and gives all apps access to write regardless of whether or not they should be able to.
SDFix is an inelegant solution that removes a layer of security, although Google’s change in how the external storage is handled was akin to cutting off a leg because your shoelace needed tightening.
SDFix may not function for you; if you don’t have system write disabled or S-OFF, you may want to consider using option #3 here.
SDFix is available for free from Google Play, although if you like what it did for you, toss the developer a donation.
Download: Google Play
