Linux SVN Repository - Raid 6

Hey everyone,

Brief rundown. I am helping with the build of a new server where I work. Here are the stats of what we currently have decided on. I am looking for some suggestions from the storage experts as to what if anything should be done differently. I am fairly new to all of the server side of things and would like to get some extra advice if possible.

Server will be used for SVN repository storage as well as a render manager and file server/storage for 3d renderings and an internal Wiki.
Linux
Software Raid 6
4 x 3TB WD Enterprise SATA Drives - We expect to expand as needed.
Base server - http://www.supermicro.com/products/s...027r-72rft.cfm
1 CPU and when needed either add in a 2nd duplicate, or upgrade both to something better if needed. Starting with: http://ark.intel.com/products/75787/...Cache-2_50-GHz
32GB ECC Registered RAM


Now at the moment, this server is only going to be used by a small team of 6-10 people. Our files can be numerous and vary in size from a few MB to a few GB. This is all based around 3D work and the per person commit can be fairly high on a daily basis. Overall we chose raid 6 because of the up time it would allow us when a drive fails. We do backups but the danger of running a raid 5 then having to rebuild for a few days with no spare drive just doesn't sit well with me.

Now I expect this to be used by around 25+ people by this time next year, so that's the main reason were going with the 2 socket board.

Main Questions for you experts:

Would you raid 6? if not, what
Does the on board raid controller need to support raid 6 if its going to be done by software?
For something of this size, up to ~6 drives x 3TB each ~18TB of storage, would a hardware raid card be a better choice than a Linux based software raid?
Is this setup close to ideal for a good compromise on safety and performance of the server performance?
Do we look high or low on CPU power for this type of usage? Would we be better off getting 2 Quads right off the bat?

I know that's kind of alot of questions, and I wasn't quite sure weather to post this in the server forum or storage, but since most of this server is being build around the storage, I figured this was better. Thanks very much guys for taking a read and any help or suggestions you can offer. :)

If Linux is a requirement, then I would stick with the LSI chip built into the mobo. Make sure you read up on the requirements for expanding the array if you do that though. You may need to make sure you have a certain amount of cache memory and a battery for it. That should mitigate some of the hit from using RAID6.
If it's mainly for storage and your software isn't limited to Linux, then I would go for FreeBSD and ZFS. This will put more strain on resources though. Now to segue to the next point.
Figuring out how much RAM/CPU you need will be mainly dependent upon what sort of requirements your render management thing needs and how much people will be hitting the wiki. Serving up some serious files doesn't take that much effort. You could probably use those drives, MD RAID, and a retired Opteron w/ 8Gb RAM and still max out GigE.