Options for scalable file storage (Windows Server)

In order to store your data properly, you have to use some additional software, since native File and Storage Services that come out of the box are not capable of consolidating the storage into single pool dispersing and replicating the data between hosts to achieve more redundancy and performance.

DFS has a lot of issues like not having the proper storage "locking" mechanics, potentially leading to split-brain in the case of network isolation, can't replicate open files and its mechanics is unable to distinguish which replica is "correct", this might lead to some issues in multi-server environments.

You can not reduce the amount of data since media data has high entropy and deduplication/compression will not work and scaling up the amount of storage on a single server is also a bad idea since should this server fail you will (temporary) lose all the data.

To transform your existing Windows-based servers into scalable storage servers that create a single shared storage pool best option would be using some software-defined storage solutions that can be installed and run directly on Windows OS:

1) StarWind VSAN https://www.starwindsoftware.com/starwind-virtual-san

Alternatively, there are good options that run as Virtual Machines on top of Hyper-V role installed:

2) HP VSA http://www8.hp.com/us/en/products/data-storage/free-vsa.html

3) EMC Unity VSA http://www.emc.com/products-solutions/trial-software-download/unity-vsa.htm

If you are OK with investing into Windows Server 2016 Datacenter edition you might be interested in

4) Storage Spaces Direct https://technet.microsoft.com/en-us/windows-server-docs/storage/storage-spaces/storage-spaces-direct-overview

If Windows is not crucial you should definitely take a look at:

5) Ceph http://ceph.com/