Overconfidence and agressive environment leads to hard rooted misconceptions getting mixed in. Like the "1gb ram per tb" rule/guideline, which only keeps getting used by people because of this forum in the old days and it agressively being presented as the truth.
I basically wrote that into the manual. The reason that this was presented as the "truth" was because we were seeing people come in with fatal pool corruptions when they had seriously mis-sized systems, and it was deemed important that this stop. It's extremely difficult to get precise debugging out of end user systems, and iXsystems wasn't interested in throwing developer resources at it to replicate the issue, because it was far outside their use case as well. Remember, FreeNAS is basically TrueNAS-ALPHA.
The worst were the AMD APU's trying to come over from FreeNAS 0.7 and use ZFS. 4GB systems were a bad thing. 8GB systems seemed to be fine as long as there wasn't a stupidly mismatched amount of disk.
So, having watched a bunch of cases of this, I noticed some trends, and then I identified some RAM sizing at which this didn't seem to be causing problems. I
specifically wrote the 1GB RAM per TB to be a bit vague. It never said, for example, whether that was per raw space, available space, or used space. The basic goal was simply not to have stupidly far off amounts of RAM, because this had been observed to cause problems. In general, ZFS needs RAM to be dimensioned larger as space goes up because the amount of metadata, metaslab free info, etc., goes up, and performance suffers when there's insufficient resources. The specifics may be different for varying use cases, but the fundamental truth is that RAM is good, don't cheap out on RAM. And if you don't give people some sort of rule of thumb, then they often try to "argue you down" as though this is just some arbitrary thing you're making up, rather than a compsci design tradeoff, which is actually what it is.
You can say that we were presenting something that wasn't necessarily "true" as a truth, because, in fact, many people did manage to run ZFS on 6GB and got away with it. But there was risk in running on low RAM, and those of us doing volunteer support work on the forum wanted users to run a safe configuration.
So,
@ornias -- should I have done something different, and if so, what?