I've recently installed Windows Server 2012 and am planning to format my 2tb hard drive with the REFS file format. Afterwards, I would like to set it up as a network drive. I understand that there are issues with reading external hard drives, or internal hard drives and partitions, between operating systems depending on the file system being used. Does this also apply to network drives (for example, can Ubuntu read a networked REFS drive)?
Assuming you will be sharing this using SMB protocol (the standard method of file sharing in Windows systems), the underlying file system is invisible to the client, and will be handled by the host machine. As such, you can format the drive in any file system that your OS can handle.
It can also be communicated to in a Unix environment via Samba, an implementation of SMB. This allows Windows machines to access, for example, an EXT partition on a Unix host. Requests from the client are sent to the server, the server itself deals with the file system and passes the required information back.