Revisiting ZFS and FreeNAS in 2019
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OK, here's my last ditch gasp to try to get you to understand my point of view:
RAID1 doesn't use parity. RAID0 doesn't use parity. So, which RAID versions do use parity, being that this is what this entire discussion is about?
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@xrobau said in Changes at Sangoma:
Now, if you want to learn more about this, please feel free to go on any of the Solaris Administration courses I have, OR, feel free to read any of the plethora of documentation on ZFS. But telling me I'm wrong isn't going to get you anywhere, because I know what I'm talking about here. This is my field of expertise.
Actually, this is mine. Telling you you are wrong isn't getting anywhere, but it doesn't change the fact that everything you think you know about RAID and ZFS is completely incorrect. I mean, honestly, this is the worst understanding of storage I've seen before. And that comes from more than a decade of these kinds of discussions. I've never seen anything this dramatic. From not knowing the basic terms you are using, to completely not knowing the basic technologies.
Just try Googling some of your stuff. And I've already provided documentation as to why you are wrong. And I've asked you to do the same. Please do so. The person making crazy claims and refuting the ENTIRE industry, including the makers of the product, is definitely the one is the "needs to provide proof" seat.
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@xrobau said in Changes at Sangoma:
So, which RAID versions do use parity, being that this is what this entire discussion is about?
RAID 2 (no existing implementation)
RAID 3 (deprecated)
RAID 4 (rare)
RAID 5 (aka RAIDZ)
RAID 6 (aka RAIDZ2)
RAID 7 (aka RAIDZ3)This is RAID 101 here. Literally the A+ requires this in the first half.
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@xrobau said in Changes at Sangoma:
RAID1 doesn't use parity. RAID0 doesn't use parity.
So let's flip it... which ZFS RAID levels are parity?
RAIDZ
RAIDZ2
RAIDZ3Which do not?
VDEV Mirroring
VDEV StripingAll information I already provided and is in countless links.
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@xrobau are the official docs enough?
https://docs.oracle.com/cd/E19253-01/819-5461/gamtu/index.html
ZFS provides a RAID-Z configuration with either single-, double-, or triple-parity fault tolerance. Single-parity RAID-Z (raidz or raidz1) is similar to RAID-5. Double-parity RAID-Z (raidz2) is similar to RAID-6.
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@scottalanmiller said in Changes at Sangoma:
RAID 2 (no existing implementation)
RAID 3 (deprecated)
RAID 4 (rare)
RAID 5 (aka RAIDZ)
RAID 6 (aka RAIDZ2)
RAID 7 (aka RAIDZ3)No. RAIDZ does not use parity. Just because people REFER to it as parity does not mean it is such. That is the 'simplification confusion'.
So yeah, sorry. There's no use continuing this discussion because you're adamant that you're correct, and you refuse to even think you could be wrong. So, being that there is no possible way for me to change you mind, there's no use me continuing, is there?
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@xrobau said in Changes at Sangoma:
No. RAIDZ does not use parity. Just because people REFER to it as parity does not mean it is such. That is the 'simplification confusion'.
It uses parity. Oracle says so, the code says so, the entire industry says so. Just making things up doesn't change that. It's not "like parity", it's standard RAID 5 parity with a variable stripe width.
And parity acts nothing like mirroring (copies), so if your claims were correct, the amount of available storage wouldn't be correct. So it's trivial for anyone who has used RAIDZ to show that it has to be parity and cannot be copying.
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@xrobau said in Changes at Sangoma:
So, being that there is no possible way for me to change you mind, there's no use me continuing, is there?
Well, start trying to change my mind by...
- Saying something rational.
- Saying something that seems crazy but at least has a REASON for your belief in it.
Right now, you are stating things we know are absolutely false, are common sense provably not true, go against ALL available documentation... and flatly refusing to provide so much as a casual reference. Basically you just called the sky red and instead of providing any reason to support why you believe it not to be blue, you are just jumping up and down screaming it is red.
So no, you've only convinced us that you made this all up and have no basis for what you are saying. The louder you yell and refuse to provide evidence (even just logic based evidence) the more it shows how likely you are to be wrong. People who are telling the truth can normally say why they believe something to be the truth. But you've not stated even where you might have gotten these ideas, let alone shown a solid foundation for them.
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@xrobau said in Changes at Sangoma:
If you don't want to work with me here, then I'm just going to not bother.
In what way have I not worked with you? I've gone point by point and shown in every single case...
- Why it is historically believed to be wrong.
- Why it goes against previously documented understanding.
- Why it doesn't make sense.
- What seems to be (where possible) the source of your confusion.
- Asked you to provide the same level of documentation that I am to support your beliefs.
Working with you is exactly what I'm doing. Everyone else seems to have written you off. I actually bothered to respond as if you were being serious about this. But you are not giving me the common courtesy of providing a single reference to any of this. Just claiming to be an expert while missing basics at an A+ level (literally) doesn't suggest that you are an expert. I knew a guy who once installed a video game from a box he bought and claimed it made him a developer because that's what he thought programming was. Doesn't make him a developer.
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Even FreeNAS doesn't say things like this. FreeNAS states very clearly that ZFS' RAIDZ is parity:
"ZFS is designed for data integrity from top to bottom. RAID-Z, the software RAID that is part of ZFS, offers single parity protection like RAID 5, but without the “write hole” vulnerability thanks to the copy-on-write architecture of ZFS. The additional levels RAID-Z2 and RAID-Z3 offer double and triple parity protection, respectively."
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@xrobau said in Changes at Sangoma:
Just because people REFER to it as parity does not mean it is such. That is the 'simplification confusion'.
So your hypothesis is that people, who all know how RAID and mirroring (copying) works, and who all know what parity is, and all know their RAID levels and know ZFS.... "simplify" by getting the term backwards? And that that makes it "simpler", why?
I think your desire to justify the belief that there is no parity is a well known parity system is leading you to concoct some truly outrageous beliefs. Simplification is the farthest thing from an explanation for the entire industry stating something complex and backwards, when what you claim to be true would be the simplest, easiest thing ever.
This just doesn't make any sense, you must see how crazy this sounds.
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Nexenta is a pretty big player in the ZFS space, they document it as parity as well...
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Here is SUN's original 2007 documentation stating that it did mirroring and parity. SUN used RAID to refer solely to parity. But notice that SUN themselves call it RAID. Statements that parity and RAID don't mean parity and RAID go a bit far. Every document that we can find anywhere all agree. And instead of providing any documentation for your position, you are just resorting to saying that all of the source documents are wrong and that none of the words, terms, or functionality means what is stated and that all of it means something other than what is said?
http://web.archive.org/web/20071015014209/http://www.sun.com/2004-0914/feature/
Also, you stated that the self healing was made possible by the copies, but even in 2007 SUN stated that the parity made self healing possible as well. So even your position that the copies are necessary for that feature are incorrect (which we knew, it's just that I now provided a specific reference for that.)
I think you should read Predictably Irrational, Revised and Expanded Edition: The Hidden Forces That Shape Our Decisions , it's a great volume for understanding how humans tend to get misinformation or a random belief and then in an attempt to justify something that we believed without foundation, will begin to formulate false reasons for it after the fact to make it seem like what we believed makes sense. If are you familiar with this process, we can see that happening in this thread.
You started with some mildly incorrect beliefs based on common marketing. Then to defend those beliefs you started adding in technical details that were incorrect, but could be chalked up to misreading some docs or overhearing something and misunderstanding. But then to defend those you just get getting crazier and crazier. As we go down through the thread, we can see the conversation devolving from simple misunderstandings to bizarre claims. By the end, you are basically calling every IT whose ever worked with ZFS a liar, like there is some secret conspiracy to make everyone confused about a really simple technology that we use every day.
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https://blogs.oracle.com/ahl/double-parity-raid-z
"Double-Parity RAID-Z
As of build 42 of OpenSolaris, RAID-Z comes in a double-parity version to complement the existing single-parity version -- and it only took about 400 additional lines of code. "
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Sigh.
@scottalanmiller said in Changes at Sangoma:
You started with some mildly incorrect beliefs based on common marketing.
I'm a sysadmin. I've done courses. This is not marketing, this is training. Now, maybe I've been trained wrong, or maybe I've forgotten my training - I was actually looking through the ZoL source code to see if I was wrong (and, it looks like I may be!), but I'm just not interested any more.
You're so hung up about HOW BLOCKS ARE STORED ON THE DISK that you've ignored everything else I've said.
So. Whatever. I'm REALLY done this time.
Oh, and here's the link to the code where they ARE doing math, which is when I was about to come in and go 'Whoops, looks like I was wrong', but turns out you're just interested in being an arsehole, rather than actually engaging in discussion.
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@xrobau said in Changes at Sangoma:
You're so hung up about HOW BLOCKS ARE STORED ON THE DISK that you've ignored everything else I've said.
But everything you've said was good, based on your beliefs of how the data was stored on the disk. That was your foundation for refuting things that we had researched thoroughly in the past.
You are acting like I'm ignoring you, that's the absolute last thing that I've done. I've paid so much attention, from the very first post.
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@xrobau said in Changes at Sangoma:
Oh, and here's the link to the code where they ARE doing math, which is when I was about to come in and go 'Whoops, looks like I was wrong', but turns out you're just interested in being an arsehole, rather than actually engaging in discussion.
How exactly am I being an ass here? I have engaged well since the beginning and worked hard, even to the point of documenting this years ago, to help educate and train. You put me in the position of having to defend the truth. You didn't believe me, or anyone, in the industry. No amount of me providing documentation helped. Then you call me an ass?
I am not the one who ignored what was written. And I'm not the one making wild claims. All I did was defend the truth and try to educate you. You had misinformation and instead of providing references, attempted to brow beat me into accepting them no matter how much they were not based on fact. You are still trying to attack me personally because I wasn't wrong and didn't let you promote a product based on a misunderstanding of it.
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@xrobau said in Changes at Sangoma:
I'm a sysadmin. I've done courses. This is not marketing, this is training. Now, maybe I've been trained wrong, or maybe I've forgotten my training
In a situation like this, we all will forget things that we don't use regularly. Even an "every day full time Solaris admin on ZFS" will potentially forget details if they aren't making RAID decisions all the time (you can implement a pre-chosen standard all the time and not have to think about exactly what it is doing or what the alternatives are.) Forgetting isn't a big deal. You gotta use very specific stuff often to have any live memory of it, normally. And the number of people implementing RAID levels or deciding between them is very small, and of that number, the number that do it often is much smaller still.
