I've been reading up on FreeNAS and RAID Z, and one of the things people kept mentioning is that you shouldn't use ZFS (or more specifically, RAID Z) on a machine without ECC RAM. I'm wondering what the reasoning behind this is. Is this an issue with RAID Z specifically? Is there any particularly heightened risk from not using ECC RAM with ZFS vs other file systems? Or is this just a general concern about corrupt memory spreading to a filesystem which would otherwise have corrected the error thanks to its support for self-healing redundant arrays?
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Why the downvote by the way? If there's anything in particular about this post which needs improvement, please let me know. Or was it more of a "you don't know enough about ECC RAM to formulate a good question on this topic" sort of thing?– Ajedi32Mar 5, 2015 at 2:46
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1ZFS requires a lot of RAM, so it does make sense to protect it from random errors. Just as you should go to RAID/ZFS when you grow data storage, you should move to ECC when system actively uses a lot of ram.– aaaaa says reinstate MonicaMar 5, 2015 at 4:05
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2forums.freenas.org/index.php?threads/… is probably worth a read– Håkan LindqvistMar 5, 2015 at 7:15
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@fukawi2 "Is there any reason ZFS or FeeeNAS specifically would require ECC memory, or suffer especially when running on a system using non-ECC memory?" Yeah, that's definitely a dup. Sorry I didn't see that before posting my question. I'd vote to close, but don't have the rep here for that yet.– Ajedi32Mar 5, 2015 at 14:05
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Mouse over the down arrow; the popup says "This question does not show any research effort; it is unclear or not useful". Downvotes without comment may be presumed to be for at least one of those reasons. And if you want to withdraw your question in the light of the dup, the delete link is at the bottom, or you can flag it for moderator attention and ask him/her to delete it.– MadHatterMar 5, 2015 at 14:40
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1 Answer
You shouldn't use non-ECC RAM on any machine that is storing or processing data you care about. This is not something that is unique to ZFS.
You're right, ZFS devs have gone to great lengths to add many layers of hashing, verification, etc. to the filesystem - all of these are of massive help in ensuring data integrity, and all of these efforts can be undermined by a single undetected single bit flip in RAM.
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Yeah, I thought that might be the case. People were mentioning it so often in the context of ZFS with RAID Z that I thought perhaps it might be a specific concern with that particular RAID configuration, I guess not though.– Ajedi32Mar 5, 2015 at 2:43