NETGEAR READYNAS PIONEER PRO
I can't say that I know, exactly, what my ReadyNAS is formatted for, but it does allow for a variety of file sharing protocols (CIFS, NFS, AFP, FTP, HTTP, and HTTPS), and the AFP, which is best for Mac users, allows me to save any files size. AFP is Apple Filing Protocol, popular in Mac environments. AFP provides better support for a larger range of characters in filenames and is preferred where this is important. I realize this does not specifically answer your question, but I frequently file share M4Vs/MP4s to my NAS that are 15 GBs, or are well over the 4GB size. Since the NAS uses a gigabit ethernet connection to transfer files, the NAS acts like another computer on your network. It runs on Linux and has a web-based control panel. When you create shares (partitions) on it, you simply indicate which of the file sharing protocols you want available, or you can have them all at the same time. I also use a PC, and leave the CIFS on, since AFP does not show up on the PC. They are the same files, it's just how it translates the file names. The NAS formats the drives automatically to whatever's best for it's operating system. So the NAS doesn't function like an external FireWire drive, but more like a server with a built-in RAID. And it's designed to work well with Macs and OS X.
READYNAS WITH ITUNES
I use my NAS for my iTunes library along with other purposes, e.g., print server, TimeMachine backup, file storage, etc. Printing and TM are services offered within the operating system and you just turn them on, but file storage is simply a partition or Share and you can create as many of these as you want by defining the size you need it to be and what file sharing protocol you prefer. In the iTunes preferences I point my iTunes Media folder location to one of these shares and as long as the Share is mounted on my desktop, it will read and write to this remote location. I also have the check boxes checked for Keep iTunes Media folder organized and Copy files to iTunesMedia folder when adding to library. This keeps the content nicely organized so I know wehere it's supposed to be. One note, if you do not have the Share mounted on your Mac desktop, iTunes will default back to your local Music folder in your Home folder. So if you have a file auto-downloading, then it won't save to the NAS, but rather your local Muisc folder. This really is no big deal, just a nuisance. Quit iTunes, Mount the Share, open iTunes and go to the preferences to confirm that the remote location is now set back to it's original setting. At least this way you don't have to reset this again, which would cause a reindex of all your files. To make sure my NAS share is mouted before I launch iTunes, I wrote an Automator app to mount it when I start up my computer. It will then stay mounted when the computer goes to sleep.
Since the NAS is networked, I can pull up my entire library on my Apple TV, or on any of my Apple devices. For Apple TV to work, however, the Mac with your iTunes library must be turned on and connected with your NAS. Apple TV reads from your iTunes database file to display all the content, rather than scan the entire library. This is something I wish Apple would change, but it keeps their customers locked in to their iTunes ecosystem and not something they will be giving up anytime soon.
NAS VS. RAID HARD DRIVE
Before I had a NAS, I had an 8-bay RAID drive with a PCI RAID card. Never again. I had a power failure and lost the entire contents of the RAID. With a NAS, you have another level of protection for your existing files. Any files being written at the time of failure, you would loose, but not everything. You must still, however, connect everything to a proper UPS. Only a simultaneous two disk failure would wipe everything out. With my setup, I have a second NAS that just backs up everything from the first NAS once a day. Belt and suspenders approach.
PROMISE PEGASUS RAID
Check out the Promise R4 or R6 if you have a Thunderbolt connection. I don't have one of these RAIDS, but been thinking of upgrading to them. They aren't a NAS, but you could set it up like a NAS with OS X Server and a spare MAC with Thunderbolt. They are RAID servers and wicked fast (think full, uncompressed HD editing in Final Cut without frame loss). Also, when you want to scale up from say 12 TBs to 36 TBs, you just buy two more R6s and daisy-chain them together. When I max out my ReadyNAS, I'll have to buy a larger box or larger hard drives to gain more space. Not as scalable as the R6.
That's it. Apologies for the long-winded answer. And BTW, I'm also no NAS RAID expert, just an enthusiast