AMD Mini-ITX Builds?

[coatmaker618]

jgreco I've been told by several mods that there's a difference between "intelligent question" and "on topic" question. Hence the concern.

It does sound like FreeNAS will pretty much use any RAM you give it, so my plan is to expand as time goes on. Maybe I start with 1x8GB stick now (or maybe 2x8 or 1x16), and buy some more later on. I'm expecting server RAM to last a while after all!

Also, why did you write the manual "vague on purpose"? It seems counter productive from this angle...what am I missing?

 

[coatmaker618]

That was my experience too. I searched high and low, and eventually gave up and bought a proper Intel server board. Asrock E3C224D2I. So far it "just works..."

tempting, especially as it's $100ish cheaper than the intel I was looking at:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157419

Plus a much better CPU selection, as I suspect atom is a bit underpowered when you need to rebuild a 4TB drive or two.

 

[joelmusicman]

Yup. It's working just golden with my Pentium G3220. I'm not happy with Plex transcoding (videos studdered when played back on my desktop, haven't tried it on plexbmc yet), but otherwise it's given me no trouble at all. Scrubs with 4TB in use take about 2.5 hours. 6x3TB Seagates, and my 1x8GB stick is fine for now. When I get around to it I'll max at 16, since I don't think this board takes 16gb sticks.

However, I might've gone the Atom route if I were buying now. The price has gone down quite a bit on that 2550 board since Jan when I bought my gear. More SATA ports and more memory capacity, less power hungry too. From what I've heard the Avoton Atoms are in a different leage compared to the old (schitty!) consumer stuff.

 

[cyberjock]

Also, why did you write the manual "vague on purpose"? It seems counter productive from this angle...what am I missing?

Not to answer for him or put words in his mouth, but many of the things are vague because not all situations require the same amount of RAM. If you want to run iSCSi and/or NFS with ESXi and you want good performance, you may need 3x+ that thumbrule. If you have 1000+ users with CIFS, you may need 3x+ the RAM. For home users, you may need significantly less than 1GB per TB.

Performance is also a major player. If performance is good enough for you, then who cares how much RAM you have as long as you have that minimum 8GB. Remember, the RAM after 8GB is pretty much only to increase performance. If you aren't happy with the performance, then you almost always need more RAM.

So the answer is vague because the question itself is vague. ;)

Another thing to keep in mind(and I have personal experience with this) is that when you start starving your system of RAM, hard drive activity will go way way up while performance continues to decrease. So you definitely don't want to play a game of minimal RAM because you're just working your hard drives harder.

 

[jgreco]

Also, why did you write the manual "vague on purpose"? It seems counter productive from this angle...what am I missing?

See cyberjock's answer. But basically your own bias is going to tend to land you at the better answer for your situation. If you're a home user you are likely to interpret that as meaning only 8GB is required for your situation. Because 20GB would seem way large for a home user. And you'd arrive at the right answer. But if you're a SMB, then you're expecting to need to spend some money, and you'll have investigated some options that are hella-expensive, and you'll know that in the storage biz, nobody means "delivered terabytes," they mean "raw terabytes" when talking about their NAS products. So you'll naturally assume 20GB is meant. And you've arrived at the right answer there too. And the home user who guesses at 20GB doesn't actually do wrong, they just end up with a more-awesome system. The only bad case is the SMB guy who guesses it means 8GB, and then we just whap him upside the head with "you need more RAM" if he complains, which even there usually they don't, because usually the RAM becomes an issue as the pool fills. Then when they really like FreeNAS and it starts getting fuller and a bit slow, then the RAM thing makes total sense and justifiable, so they just add it as needed.

It is basically a cheaty way for me to have my cake and eat it too when talking about RAM requirements in the forum, because the meaning is a bit malleable. It is productive for _me_ because I can minimize the inevitable battle with some clueless twerp who desperately wants A when B is the better answer. You KNOW there'll be some SMB guy who can't wrap his head around the 20GB and wants to do 8GB "because the docs say that will be fine for a home user!". We just say "fine, reduced performance, enjoy" and move on. And it even works for him.

 

[coatmaker618]

Ok, I gotcha. It's not directly a question of stability, but really of performance. Of course, lower performance in a NAS means more swapping, which does raise the bar for stability issues a bit (especially over time).

So it really seems like the best way to answer would be to get a nice comparison chart, showing how much RAM usage/swapping is occurring per quantity of RAM (of course, this would only be valid for the same MoBo/CPU/ disk setup). Since that's non-trivial I expect that the best test will be in how long it takes to build the my 5 disk array into a ZFS3.

 

[jgreco]

No, it isn't swapping. ZFS ARC is kernel space, not user.

 

[cyberjock]

coatmaker618:

Actually, disk usage goes up in the pool because the caching system can't retain its required information before it will need it again, and performance plummets. It actually had nothing to do with swap(which is what I thought at first). And since the pool was reading massive quantities of data when trying to do something as simple as open a 5MB file I was convinced that it *had* to be swapping. No, the caching system just went to crap.

Here's a simple way to think about the RAM thing:

-The 2GB of RAM with UFS and 8GB of RAM is strictly for stability.
-The 1GB per TB of disk space is strictly for performance.

 

[coatmaker618]

cyberjock thanks. That's sorta how I was interpreting those two rules, but it's good to have it laid out like that :)

also I didn't even think about caching, but that's unfortunate! Sounds like a more dynamic caching size would be useful.

 

[jgreco]

Sounds like a more dynamic caching size would be useful.

The Adaptive Replacement Cache is designed to use as much of the system as is practical; the problem is that ZFS was designed from the beginning to run on a system that's ... large.

Sun looked at the evolution of FFS, and recognized that they are building a filesystem for the /next/ quarter century. They knew that if they made design decisions such as making effective use of tons more RAM, eventually even much larger base requirements would not be onerous.

Put differently, we can complain today that FreeBSD can no longer be booted on 4MB RAM systems. But the tradeoff is probably fair.

 

[coatmaker618]

jgreco assuming FFS == Fast File System not the other 'ffs' :p

I gotcha, guessing it won't be too happy on an 8086 either!