8GB of RAM Sufficient for This System (for now)?

[cmfisher4]

All,
I have my case (Define R4), my mobo (X9SCM-F-O), my CPU (i3-3220) and my PSU (Antec 450 Green). I intend to purchase 4x3TB WD Reds (RAIDZ2) but only 8GB (1x8GB) of ECC (expanding to 16GB (2x8GB) when I save up the money. Out of the 5.5TB of usable storage this will give me, I will be using less than half of that (about 1.8TB) and should still come in at just about 50% utilization when I am ready to purchase the second 8GB in a month or two.
I have been running FreeNAS 9.1.1 on a test machine to learn the ins and outs have it stable enough for what I need it to do (home file/media server) that I am ready to build my "production" rig. The hardware specs (Phenom II X4 955, 8GB of RAM but only 2x160GB HDDs in ZFS mirror) of my test machine do not allow me, I believe, to correlate it to the performance of my intended build above.
I've read jgreco's hardware recommendation post (and the rest of the conversation) that says to essentially just go with 16GB because it's cheap. But I've also read the official Docs which say 1GB for 1TB (I assumed this means total drive capacity, not usable because otherwise my question is stupid) but that this can be stretched for home use. I haven't been able to find any hard numbers on performance but several (thanks cyberjock) anecdotal comments on the performance "crash" when your RAM just isn't enough anymore.
My question is, in your opinion, can I stretch this thumbrule to what I want to build above and not negatively impact performance to the point where I get frustrated that I didn't wait. I am running a Win8 based system now that is performing the duties of a server and I am content with it, but would like to get my data into a more reliable environment.
Thanks,
Chris

 

[warri]

I think you will be fine with 8 GB for now, it should give you a stable system.
The performance impact depends on the load you want to put on the server (how many concurrent clients? which protocols? etc).

 

[cmfisher4]

warri,
Thanks for the reply. I would be running CIFS shares for windows-only clients. Probably only streaming video (1080p) to one client and serving files to one other and usually not at the same time.

 

[warri]

In this case you'll definitely be fine. For comparison: My setup is very low-end and works fine for streaming 1080p to one client via CIFS.

 

[Johhhn]

fwiw, my test build is a 2.5ghz core duo with 4GB RAM, and 4x2GB in RAID10 and besides some stability issues with AFP/TimeMachine, it's quite fast and maxes out my gigabit fairly easily.

 

[jgreco]

You'll be fine. The recommendation on the documentation site is deliberately a little bit vague on whether it means total, usable, or even used capacity (and since I deliberately worded it that way, I assure you that was quite intentional). We are primarily concerned about stability and yours should be stable. 16GB could make it faster, depending on workload. 8GB is the floor for stability, with additional strongly suggested - and for sufficiently large pools, ultimately required.

 

[DrKK]

You are 100% fine with 8GB here. I don't even think you need to "save up" to go to 16GB. I'm running 8GB on my 3x2TB system (SuperMicro X10SLM+-F by the way), and I'm not even remotely tempted to upgrade to 16GB. I am getting pretty much maximum performance across the board, and no stability issues of any kind.

 

[cmfisher4]

All good to know data points! Thanks, everyone.