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Comment by ianai | Hacker News Reader

I stand corrected, sorry everybody.

ZFS without ECC Ram isn't as dangerous as you might think. http://jrs-s.net/2015/02/03/will-zfs-and-non-ecc-ram-kill-yo...

"There’s nothing special about ZFS that requires/encourages the use of ECC RAM more so than any other filesystem." -Matthew Ahrens (Cofounder of ZFS at Sun Microsystems and current ZFS developer at Delphix)

Well, this hurt, but I learned something today. Thank you.

It's a common myth being repeated.

I think comes from an assumption that if you use ZFS you care more than users of other filesystems about getting the same data you have put onto disk out of the disk later when reading it back.

If that's important it's good advice to use ECC RAM. The point that's often lost is that if you cared about correct data, then having ECC RAM would have been a good idea regardless of using ZFS or not, and you're not worse off with ZFS than you would have been with another filesystem without ECC RAM.

Another common myth is that ZFS requires large amounts of RAM. It doesn't do that either, but the assumption is that if you use ZFS you're building some large multi-user system which benefits from a large cache. If that's not your use-case then that's not true, you could run ZFS on your single disk laptop if you wanted to.

Coincidentally both myths originate from the FreeNAS forum.

If you can afford ECC then that is obviously preferable. However the horror stories regarding running ZFS on non-ECC are greatly exaggerated.

s/exaggerated/wrong

Not merely exaggerated, nonsense. All filesystems using non ecc memory are more likely to experience damage to the data stored therein.

Zfs is no more likely to be damaged that anything else.

This whole confusion stems from zfs devs suggestion that ecc ram be used and people who don't know any better thinking oh that must be some special requirement for zfs.

These folks then spread this misinformation all over the Internet where its passed on by people who know nothing about the topic.

Pro tip: don't talk about things on the Internet that you only know about 3rd or 37th hand. If you know nothing about the topic you aren't improving the store of human knowledge by passing on noise.

> Not merely exaggerated, nonsense. All filesystems using non ecc memory are more likely to experience damage to the data stored therein.

If it were "nonsense" then one could flip the argument and say "ECC memory has no beneficial effect what-so-ever" - which be both know is untrue. However I can see why people do say "nonsense" given the ECC-myth seems to only be discussed in relation to ZFS and the probability data errors due to non-ECC memory is small.

For what it's worth, I did originally include a comment about how the risk being the same as on any other file systems - but then deleted it fearing I might have overlooked something on another fs I'm less familiar with.

> Pro tip: don't talk about things on the Internet that you only know about 3rd or 37th hand. If you know nothing about the topic you aren't improving the store of human knowledge by passing on noise.

I don't think that's fair. The problem with 1st hand experience is that it's often just based on anecdote. Which can often be worse than 3rd hand advice. And in the case of failures: often some products are too widely used to be worth constantly badgering the development team for help; which means you end up having to rely on the advice of others. The problem is really more that some people are terrible at researching so take 3rd hand advice without bothering to fact checking it.

In any case, I don't know if your comment was aimed at me or not, but I do have nearly 10 years of experience (wow that's gone quick!) running ZFS across a variety of systems, some running ECC memory, others not. I've also been a keen study of the Sun/Oracle docs. So I do consider myself reasonably well informed from both credible sources and personal experience. Though I'm not arrogant enough to assume I'm an expert either - communities like HN can be deeply humbling places.

> > Not merely exaggerated, nonsense. All filesystems using non ecc memory are more likely to experience damage to the data stored therein.

> If it were "nonsense" then one could flip the argument and say "ECC memory has no beneficial effect what-so-ever" - which be both know is untrue.

The original argument is like an implication ("no ECC => don't use ZFS"), which he refutes by saying (correctly), that file systems are generally affected the same way by memory corruption. Your argument seems to invert the original implication and drawing conclusions from that (fallacy of the converse, I believe). ∎

He was refuting my "greatly exaggerated" remark by going on to make the same points I was alluding to albeit directly and in more detail. So I was in turn elaborating on my choice of language.

I feel between this post and you're previous one that you are basically just agreeing with me via the process of nitpicking the language I used.

We used to say that the fastest way to get a good answer is to post a wrong assertion on Usenet.

I learned to do that in academia, too. It's effective but you need your flame retardant boots on.

I don't understand how you could think this. It's not merely the fact that it's incorrect I don't understand the line of logic that would lead to the conclusion that zfs requires any more sophisticated setup or ecc to function.

Furthermore backups and raid may be related but they are pretty orthogonal. Having a reasonable strategy to ensure performance integrity and reliability isn't obviated by having a good backup strategy.

If you have to restore from backup aren't you going to lose some amount of data even if it's only the last hour -> day.

There is no reason not to run ZFS on non-ECC memory, let alone it being "insane".

triple negation? Surely this isn't needed...

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