FreeNAS ZFS questions about CPU, Ram, & HD speed

Question

I'd like to build the most energy efficient NAS possible but still be able to run FreeNAS with ZFS.

• I've been looking at Atom processors, but haven't found any that could support more than 4gb of ram. Is ATOM fastest enough to handle a 3-5 harddrive ~10TB NAS (mostly for drop storage movies, photos, etc.)? I've read you should have ~1gb or ram per tb of disk (ZFS). Is an Atom powered (4GB Ram) NAS unrealistic?

• Second question, for the harddrives what should be my minimum requirements? IE Would 5400, 5900 vs 7200RPM or SATA 3.0/6.0/gb/s make a tangible difference for this purpose?

Solution 1

Regarding the maximum RAM: There are Boards with Atom-CPUs supporting 8 GB RAM: Asrock AD525PV3

I haven't found a pattern (NM10 chipset or ION), but occasionally some boards do...

Solution 2

1gb or ram per tb of disk

Ideally, ZFS requires about 2GB of memory for each TB of storage only if deduplication is enabled, because of the relatively large deduplication table. 1GB of memory per TB is probably overkill otherwise, especially for typical home server use. Also, FreeNAS 8 only supports v15 of ZFS, which does not include deduplication support.

Faster RPM drives have better random read/write speeds, at at the cost of higher power consumption. If performance is important to you, then that is your answer.

Solution 3

I have a Freenas box running from a Celeron processor that is just slightly faster than the average desktop Atom.

Mine handles 4 hard drives just fine - remember that file operations are not CPU intensive, that is handled separately by the I/O controller.

The CPU will only be used if you choose to use Software Raid, and on my box, I stream movies all the time and the CPU barely goes above 20%, so, I am sure you will be fine.

As for hard drive speeds, this is a very hard one. 5400RPM drives will use up less electricity, but, it is possible for it to slow down write activities across the network (read/heavy copying as well, but, it should be fast enough for streaming and regular stuff). Only you can decide this. I personally went for 7200RPM drives on mine.

Comments

[Genina Anne Gabuten]

Yes, I will be using the software based RAID, but that sounds great. I was thinking about 5900 as for many of the "Green" drives it seems to be a lucky number. Thanks!

[dmitry.tcheban]

Yes, but does FreeNAS amd64 run on an Atom? Because FreeNAS i386 will have a 4GB memory limit.