First FreeNAS build

[seedzero]

So I've just purchased a case for my first FreeNAS build (U-NAS NSC-810A), and I'm finalising the components to assemble inside the chassis. At the moment I'm looking at:

CPU: Intel - Core i3-6100 3.7GHz Dual-Core Processor
CPU Cooler: Noctua - NH-L9i 33.8 CFM CPU Cooler
Motherboard: Supermicro - MBD-X11SSM-F Micro ATX LGA1151 Motherboard
Memory: Crucial 16GB DDR4-2133 PC4-17000 ECC Unbuffered 288-pin EUDIMM
Storage: 5 x Western Digital - Red 6TB 3.5" 5400RPM Internal Hard Drive

I'll be using RAIDZ2. Will 16GB of RAM be enough? Mainly used for media storage, maybe some very light transcoding. Thanks in advance.

 

[Plexxie]

I can't really give you advice about the other parts but for HDD you should get the BestBuy easystore 8TB external for 149.99 each right now and shuck them to get 8TB WD white/red internal drives to use for NAS. That's what I have for my in-progress FreeNAS build Norco-RPC 4224 with 24 x 8TB.
https://www.bestbuy.com/site/wd-eas...-3-0-hard-drive-black/5792401.p?skuId=5792401

You save at least 100 bucks per drive AND you get 2TB more. So you'll save at least 600 bucks while getting 12TB more. You can use that 600 bucks to buy about 4 more 8TB drives for an additional 32TB!

 

[seedzero]

Thanks for the advice, unfortunately no BestBuy here as I'm located in Australia. :(

 

[Plexxie]

Oops my bad, didn't realize you're in Australia.

 

[Jeff Chen]

I remember reading somewhere that you really should do even numbers for Z2 (and odd numbers for Z), otherwise you would be wasting space or suffering from weird performance issues.

 

[anmnz]

I remember reading somewhere that you really should do even numbers for Z2 (and odd numbers for Z), otherwise you would be wasting space or suffering from weird performance issues.

No. Ignore this advice. To quote Matt Ahrens:

Choose a RAID-Z stripe width based on your IOPS needs and the amount of space you are willing to devote to parity information. If you need more IOPS, use fewer disks per stripe. If you need more usable space, use more disks per stripe. Trying to optimize your RAID-Z stripe width based on exact numbers is irrelevant in nearly all cases.

Fully explained in the blog post:
https://www.delphix.com/blog/delphi...or-how-i-learned-stop-worrying-and-love-raidz

(BTW the term "stripe width" here means "number of disks in your RAIDZ vdev".)

 

[seedzero]

So will 16GB of RAM be enough for my use case? RAM is pretty expensive at the moment, and the cost of the build has already crept up

 

[anmnz]

So will 16GB of RAM be enough for my use case?

16GB should be fine for storage plus a bit of processing. You haven't mentioned anything that would suggest you need more than that.

 

[Jeff Chen]

No. Ignore this advice. To quote Matt Ahrens:


Fully explained in the blog post:
https://www.delphix.com/blog/delphi...or-how-i-learned-stop-worrying-and-love-raidz

(BTW the term "stripe width" here means "number of disks in your RAIDZ vdev".)

Thanks for clarifying that. There are too many myths floating around that scare newbies like us. Yesterday I just saw someone stating that FreeNAS “requires ECC RAM or you could lose all your data to scrubbing”... At least that one was busted already.

 

[Jeff Chen]

So will 16GB of RAM be enough for my use case? RAM is pretty expensive at the moment, and the cost of the build has already crept up

You should be fine but don’t be surprised when some hundreds of swap is used occasionally when things get too intense sometimes.

Just a side note: I was fooling around and enabled auto-tunables earlier, and that gave me some headaches on memory/swap.

 

[Chris Moore]

Thanks for clarifying that. There are too many myths floating around that scare newbies like us. Yesterday I just saw someone stating that FreeNAS “requires ECC RAM or you could lose all your data to scrubbing”... At least that one was busted already.

Also, some things have changed over time, but the historical information gets mixed up with what is currently true.

I was fooling around and enabled auto-tunables earlier, and that gave me some headaches on memory/swap.

Auto tune can be too aggressive with some settings and it doesn't account for things like jails needing memory. I had autotune on for several years but I turned it off and made some changes by hand. One thing you can set if you want to try to prevent use of swap, is the tunable called, "vfs.zfs.arc_max". You probably want to set that four GB less that your total amount of RAM so you have room for the OS. If you are running something like Plex media server in a jail, give that another 2GB. That would mean reserving 6GB for program execution and 10GB would go to ARC. The number for the tunable is in bytes if I recall.

 

[Jeff Chen]

Auto tune can be too aggressive with some settings and it doesn't account for things like jails needing memory. I had autotune on for several years but I turned it off and made some changes by hand. One thing you can set if you want to try to prevent use of swap, is the tunable called, "vfs.zfs.arc_max". You probably want to set that four GB less that your total amount of RAM so you have room for the OS. If you are running something like Plex media server in a jail, give that another 2GB. That would mean reserving 6GB for program execution and 10GB would go to ARC. The number for the tunable is in bytes if I recall.

That was definitely the case. I think the system defaults actually do a reasonable good job on keeping the ARC size in check. As soon as I turned off auto-tune and deleted those entries, everything went back to normal. And the "wired" part of memory has always been 4-5GB less than the total amount.

Though my next step should still be downloading buying even more RAM (when the prices go down a little bit). I plan to start toying my FreeNAS box with XenServer and it won't be a light workload.