Hey!
Just to elaborate a bit about what Herr_Merlin said, there are a few potential issues to be aware of with FreeNAS on that hardware. It should work (and none of these issues are fatal if it's an archival system that's regularly backed up), but you're a little bit off the beaten path. Just going down your parts list:
- The motherboard in the EliteDesk doesn't support ECC RAM, which isn't optimal for FreeNAS and ZFS. ZFS doesn't require ECC any more than any other filesystem, but it takes a lot of steps to ensure data integrity and the conventional wisdom is that it's a bit silly to hamstring it by going with non-ECC RAM. That being said, if you're aware of what you're giving up and are clear on your purpose (it sounds like you are) it's not fatal. As well, there are occasionally issues with consumer motherboards and their SATA controllers and NICs. Because the EliteDesk is a business desktop you might avoid those problems, but I'd do some validation, especially on the SATA controller, just to make sure. At worst, both those problems can be solved with a $15 Intel gigabit NIC and a $25-$50 LSI HBA variant.
- Your CPU also doesn't support ECC, but unless you're planning on throwing it in a motherboard that does it's sorta a moot point. It's overpowered for what you're asking of it, but it'll work well enough.
- RAM/L2ARC (cache) drive: This is the place where I think your build is most out of whack, but it's in a way that'll make this whole thing cheaper, in all likelihood. ZFS uses RAM for ARC, ZFS's caching system. This is why you always hear about how ZFS loves RAM--that's where it stores its cache, not on disk, and more ARC means that your system is generally more responsive. Adding RAM is going to be the single best thing you can do for performance. You can add a fast SSD as secondary ARC (called L2ARC), but this tends to be a bad idea if you haven't first maxed out your RAM. Even the fastest SSDs are dramatically slower than RAM, and L2ARC actually uses some of your ARC to index itself, which actually reduces performance in most applications. There are very, very few scenarios where an L2ARC is genuinely beneficial, and an archive server probably isn't one of them. That being said, Herr_Merlin is right that you shouldn't (and maybe can't) put L2ARC on your boot drive. (Also, if you were going to use L2ARC, the drive doesn't need to have power loss protection--it's just a read cache, and no data is ever only stored there. The SLOG is a different story, but again, one of those isn't going to be useful for this application.)
- One thing to consider about your drives is their heat output and cooling. NAS-focused drives can throw out a lot of heat, and it's worth making sure this case can actually cool them adequately. Another thing to add into the validation process.
- For your boot drive, most folks get the smallest, cheapest SATA SSD they can and call it a day. It doesn't need to be particularly zippy for a SSD, and it doesn't need to be particularly large (32 GB will do). Folks boot off mirrored flash drives with success, if that gives you any insight into the requirements here.
All in all, it's a workable build for home use, and a relatively decent build for archival use in an office. If you're wedded to it, it'll work okay. However, I'd encourage you to take a look at the hardware recommendations guide posted in the resources section of the forum, if only to get a sense of what compromises you're making by going with this setup over something more purpose-built. Especially in an office setting where reliability is at a premium, it might be worth your while to go with a more robust solution.
(As a side note, if you already have a rack for your Nimble and a dedicated room for it, it might be worth looking into a used server based on the Supermicro CSE-846. They make great--if a little loud--storage systems, and have 24 bays, which should give you more than enough room to expand in the future if need be. In the US systems based on Sandy Bridge-era Xeons are around $400, and are a pretty capable system for your purposes and basically the gold standard of FreeNAS hardware. It's more expensive than free, but depending on your needs it may be what you're looking for.)
