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What factors should you consider when choosing a CPU for a FreeNAS server? What are the implications and limitations based on CPU in this context?

Currently I'm looking to build a FreeNAS server with 4x 3TB drives in RAID5 that would be accessed by 1-2 users and I am unsure about what CPU to go for.

I am considering a G530 but don't know if there would be any benefit in a better processor?

Other options include G620/G630, G840/G850/G860, and i3 2120. Would the G530 be insufficient? Would the i3 be overkill?

The server will be fitted with 16GB 1333MHz DDR3 RAM.

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up vote 2 down vote accepted

For a simple NAS server just storing files:

  • A simple, cheap, low power CPU will do fine.
  • Your network is probably going to be the bottleneck
  • Try to use low power green (Or WD red) drives.
  • Not much RAM is needed (it might speed things up slightly. But if your bottleneck is not disk access but transfering stuff via the network then this will not help much).

For a NAS with ZFS filesystems:

  • Get more RAM (4+ GB)
  • Get a 64bit CPU

For a NAS with encryption:

  • Either get a HW support or a much faster CPU
  • Try to match the used encryption with CPU features (for both speed and less power usage).
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(Slyghtly offtopic) Whats the real advantages of ZFS over (eg.) EXT4 in the case of the user? Just the "data integrity verification against data corruption"? Just asking, i never used ZFS ;) – Cláudio Pereira Aug 19 '12 at 11:59
In the documentation for FreeNAS they suggest 1GB of RAM per TB of storage. Is this much not needed? (I was planning on getting 16GB as it is not much more expensive buying a double 8GB pack opposed to 8GB + 4GB individually.) – Mitch Satchwell Aug 19 '12 at 12:10
The advantages of ZFS over other file systems depend on the features used. If you just store data you have the additional integrity checks. But you enable also enable things like de-duplication or RAIDZ. And that will cause it to use more resources. – Hennes Aug 19 '12 at 13:06
@mitch You can get away with much less RAM, but ZFS can be quite hungry and the FreeBSD mailing lists had quite some problem posts with ZFS with low RAM or a 32 bit kernel. I would stress to get a 64bit CPU, but all CPU's mentioned (G530/G620/G630/G840/G850/i3 2120.) are already 64bit capable. So that part is covered. – Hennes Aug 19 '12 at 13:19

Even an atom is enought for a NAS. It just stores things!

I have a 1250Gb NAS running with one 500Mb DDR2 stick (to save power), and a old C2D@1.8Ghz with undervoltage applied. The average load is like 0.02...

100€ of old hardware is more than enough for what you want, don't waste good hardware!

PS: Before you say that you do more than storage(if you do), i run apache, php, mysql, squid, sshd and obviously ftpd, simultaneously with the load i said before.

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Won't be used for anything other than a fileserver. Sounds like the G530 should do the job then, thanks. – Mitch Satchwell Aug 19 '12 at 11:51
@MitchSatchwell When you find the answer you need you should mark it as the answer for the question. – Cláudio Pereira Aug 19 '12 at 11:56
I know, waiting to see any other answers first. – Mitch Satchwell Aug 19 '12 at 12:06

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