If you are running anything less than 8.6.1 on your UC box, check your flash storage usage and upgrade before you run out of space.

I got hit with this and lost all of our voicemails frown

More info here: https://supportforums.cisco.com/message/3833195

The scary part of this is how many of these boxes are installed in small businesses without any sort of knowledgeable IT staff on hand. Hiring outside help to fix a busted box and upgrade would be quite costly. How many of them regularly back up their voice mails too? Probably near zero.