I actually have one of these servers (purchased about 14 months ago) running FreeNAS 9.3 in an enterprise environment. If you haven't already purchased your unit, I would offer the following advice... 1) These servers were custom built by Dell for big data centers and although they are based off of Dell's C2100 line, they are NOT officially supported by dell. I've found that getting the hardware to work isn't really a problem, but you're not going to be able to upgrade the BIOS or the IPMI firmware. I've spent hours looking for compatible upgrades and they just don't seem to exist. Again, as long as the server is working out of the box this might not be an issue for you.
2) These units run HOT and they are extremely LOUD! I can't imagine any home setting where this thing wouldn't be a nuisance. Adding this single server raised the temperature in my server closet (with a dedicated AC unit) by almost 4 degrees and made a very noticeable difference in volume in a rack that already contained 3 Dell R710's, 2 R310's, an 1850, and a T620. If you have a completely dedicated closet in the basement with adequate cooling you might* be ok using this in your home, but don't think you're just going to stash it under the desk and forget about it.
NOTE: if you or anyone else reading this thread is planning on rack mounting this unit, plan on using 3U of space even though the server itself is only 2U if you're going to be using all 12 drive bays. Packing 12 3.5" drives in the front of this thing didn't leave much room for airflow and Dell actually put a perforated vent on the top of the chassis right behind the backplane. My processor temps dropped 10-15 degrees by leaving an open space above the server so that the fans could pull air in through this vent.
3) Forget about using the Perc 6i RAID card that come with these. Yes you can get it to work w/ ZFS by creating 12 RAID0 'arrays' but just don't do it! This card won't pass SMART data or any of the other information ZFS needs to properly do it's job. Listen to the forums and get an IBM M1015 crossflashed to IT mode and be done with it. (You can get these cards for around $80 on eBay if you look hard enough) Do keep in mind though that the backplane in these servers usese the older SFF-8484 connector while pretty much all of the LSI based HBA's have dual SFF-8087 connectors. I bought a cheap SFF-8484 to SFF-8087 cable on eBay that caused all sorts of weird errors when placed under load. If you end up going this route, plan on spending $25-30 for a quality cable.
4) While we're on the topic of the backplane, because it has a single data port, you're only going to be able to take advantage of one of the ports on your shiny new HBA. Also, some of the ports on the backplane seem limited to 150 Mb/sec transfer rates with this setup. In a home setting this probably won't be an issue for you, but it is something to keep in mind. (I'm actually planning to upgrade my backplane to one from a newer Dell FS12-TY model that has dual SFF-8087 connectors and will allow all the drives to connect at 300 Mb/sec - $107 on eBay)
5) Last item is RAM - My unit also shipped with 24GB of ram with all 6 slots containing 4GB modules. This will probably be plenty for home use, but do keep in mind that ZFS absolutely loves RAM and 24GB really isn't enough if you cram this thing full of large capacity drives. (Rule of thumb with FreeNAS is 6 GB + 1 GB for every TB of raw storage you put into it) Since all 6 slots will most likely already be full, it's going to be pricey to upgrade in the future.
To summarize, this server can and does work with FreeNAS/FreeBSD but only if you're willing to put in some work and are ok with it's limitations. And I absolutely would not recommend it for a home based set-up in any circumstance. I've actually replaced my production server with a newer Dell FS12-TY (18 DDR3 mem slots and a better backplane) and moved the FS12-SC unit into a backup/fail-over role. Because of the advantages they offer, I would highly recommend anyone looking to purchase one of these for FreeNAS try to find one of the TY models.
Final word of caution, you didn't mention exactly what you were planning on using Proxmox for, but I would have to say that running FreeNAS virtualized is a terrible idea. I would suggest running FreeNAS as your base OS and then adding server roles using Jails instead. The FreeNAS forums are filled with people who lost data by trying to run on a virtual platform - just don't do it!!!!
