Just having the system operate is not the same as running the MemTest86 on it. Lets say you get one full pass and then build up your system, well I'd still go ahead and run MemTest86 for a few more days, and also you should run a CPU stress test for about 30 minutes or so. Everyone has an opinion on how long a CPU stress test should run, mine is 30 minutes. If your system craps out during this test then post those results.
I had Memtest86 go through three passes in a 24 hour period without any issues. I believe that
Memtest86 v6.3 also tested across all eight threads/four cores of the Xeon Processor. Based upon my testing for my own personal use, I am satisfied with the results. Would it benefit from further testing? Yes, it would. I'm backed into a corner though because I believe in backups for my systems.
Previously, I was testing out FreeNAS on a old Dell OptiPlex 755 with a Intel Core 2 Duo E6850 on a experimental basis. It was a old work box with an old single 1TB hard drive and 8GB of non-ECC memory (out of 8GB) available. Anyone who is somewhat experienced with FreeNAS builds can name a dozen things wrong with this configuration. However, it was "good enough" for me to put automated weekly whole drive backups on from Acronis True Image. It was "good enough" to actually learn how to use FreeNAS and get some experience so that I know what to expect. It was, however, not "good enough" to store non-replaceable data because of the known limitations.
I had planned on doing this build at the end of the year, not now. It got accelerated because the "experimental" box had a fan failure in late April. Not of the hard drive, not of the memory, but because of a stupid fan that was mounted in the front that would have cost more in effort that it was worth to disassemble and repair. From late-April until now, I have not had regular backups of my main computer, my personal laptop, my multimedia computer, or my mother's laptop. Any backups (haha) involved hooking up a portable hard drive. It is much easier to automate the backups to a NAS drive, then copy the data to a external drive every month. Because of that "major issue" (for me),
However, even though the memory, processor, case, and m.2 boot drive is in a finalized state, I am running with a old single 2TB drive from 2009 because I am unable to afford the drives that I want. There is no RAID redundency. Because of that single point of failure, I still classify my FreeNAS setup as "experimental". But, it's a personal NAS, and it is "good enough" for what I need to do right now.
Also, larger CPU coolers place more stress on the motherboard and mounting assembly, especially when you set the computer down a bit hard or just transport it from one place to another. You will do what you desire, that's fine, I just wanted to let you know that the boxed CPU cooler is nice and light and does the job very well.
With all due respect.... once the final assembly takes place, the FreeNAS server will be sitting in the corner collecting dust. I prefer the larger heatsink because if the fan fails, I still have an allowance for passive cooling.