Sadly, moving my productions to Linux isn't something I've thought about in a long, long time ... maybe I should. I'm currently on Avid Protools 12 with Apogee converters. I dumped the DigiDesign PCI-X hardware a few years back but I know for certain there was no Linux support there. In fact, Linux just listed it all as unknown devices. Kind of sad. I had a couple of firewire 002's and 003's that again, Linux didn't recognize. The old Motu 8pre's were seen by the system for what they were but again, not supported even as a basic audio device and Audacity couldn't do anything with them. Same with the Presonus gear. The closest I ever got was with a Mackie Onyx and the USB interface and it was in fact recognized as a USB audio interface and Audacity would record from it but it was not good audio and, in the end it was a single channel recording - just no support. I toyed with the idea of poking around in the device drivers however a friend at Avid (shortly after the DigiDesign acquisition) told me there would almost certainly be a DMCA takedown order if I went down that road so I never did. That was back in the PT73 days playing with Fedora Core 3/5. And then along came the iLok. I don't recall ever plugging that into a Linux box. Personally I would love to see some DAW's coming up on Linux! There are so many RTOS kernels out there and even with the high end hardware, software and converters and such - the lag time imposed by the OS (pick flavor) and all the little restrictive hiccups could possibly go away!

Build it, all the way! But, do the research first - make sure you know what you're getting but more importantly make sure you're getting what you really want!

Well, your question leaves out a lot of details but from what you've said so far, look at getting some new hardware in there and start virtualizing some of the the EoL systems. This will provide you an upgrade path for existing systems and a snapshot'd point of restore in the event of a failure.

I am a professional and manage several hundred petabytes globally. From experience I can tell you, they may be asking for half petabyte right now but tomorrow that will double and again next year and so on. Plan big to start with and you'll save your future self a lot of grief! If you PM me I can give you more details but in short I can suggest:

1) Look at a scalable filesystem like GPFS or StorNext. Yes there is a price tag associated with big iron filesystems (and no I don't work for any of them) but you get what you pay for, and scalability is everything. As an example - pairing GPFS with TSM and the right hardware, I can create an infinitely scalable filesystem that'll scale to yodabytes.

2) Tier the storage system. Think SSD for the cache (here and now) I/O, winchester disk for the short term and tape for the long term. Yes, tape: compute cost per tb on tapes the vault versus square footage in the data center.

3) Separate your networks. Keep the client access separated from the disk i/o. Doing this will save massive congestion problems from day one!

There are lots of other things to consider but by today's standards a half petabyte isn't an insurmountable amount of data just like a terabyte was twenty years ago.