My big rule of thumb is not to store anything directly on the DMM. There is backup capability in the DMM administration and it gives you the ability to back up content to a seperate location. DMM is for command and control and is not positioned as a media server although it does have thos capabilities and servers running in the back ground. Best practices says use external storage for media content and files.
As you grow your media deployment you will find that knowing what is where and how much media is out on the edge of the networkand stored where to become more of a pain to manage.Backing it all up becomes a whole project in itself. The DMM does give you some rudimentary capabilities here but ...
Actually how you go about it all depends on the make up and size of your network and the deployment and your plans for growth. Anywhere and anytime you can centralize content in the cloud it is benefitial but that may not be possible. Explore ACNS / WaaS and the ability it gives you in using cifs storage. At the very least you can look at using Apache servers and Wowza media servers set up to deploy apps to your DMPs from a central location.That is inexpensive to set up as a first step. I would suggest you contact a Cisco Partner to perform a Medianet Assessment and help you draft a content stategy for your deployment. That could be as simple or as complex as the size of your deployment and complexity of your network I hope that helps
Cheers
C.O. Little.
