About ZFS, primer video link (By Level1Tech and Wendell)

Bikerchris

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danb35

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Interesting. At 9:19 in the video, I think I see the source of the misconception (that I've addressed a number of times here recently) that RAIDZn uses dedicated parity disks (which of course it doesn't; parity is spread across all disks in the vdev). If I had a criticism, it'd be that it's much more theoretical/philosophical than practical--it gives a lot of information about the history and goals of ZFS, it's fairly light on how it works, and despite the promise in the introduction, gives almost nothing in the way of comparison to btrfs or anything else.
 

Bikerchris

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Interesting. At 9:19 in the video, I think I see the source of the misconception (that I've addressed a number of times here recently) that RAIDZn uses dedicated parity disks (which of course it doesn't; parity is spread across all disks in the vdev). If I had a criticism, it'd be that it's much more theoretical/philosophical than practical--it gives a lot of information about the history and goals of ZFS, it's fairly light on how it works, and despite the promise in the introduction, gives almost nothing in the way of comparison to btrfs or anything else.
I've got to say, I do like Wendell but you're right, I suppose it was more philosophical than practical use. Still, a good intro for some I'm sure.
 

NickF

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Wendell was mostly introducing the concept at a high level. It's not really fair that you're criticism is around the fact that he did not go into the weeds as much as you thought he should have.

As far as the parity thing, yeah the graphic is an incorrect oversimplification. But he has stated in other ZFS videos that it doesn't really work that way. He's trying to use words and concepts that the uninitiated can follow.
 

danb35

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It's not really fair that you're criticism is around the fact that he did not go into the weeds as much as you thought he should have.
I think it's a valid criticism. As interesting as the video and the history are, I don't think they're going to be especially helpful for a n00b who's trying to set up a sensible ZFS pool. And I think (based both on the text Bikerchris wrote, and the place he posted it) that's how he intended it to be used (regardless of what Wendell may have intended). For that purpose, I think there are other resources that would be more helpful (many of which are already posted here). If you want an overview of the history of ZFS and what it's designed to accomplish, great. If you want to understand how to make it work for you, there are probably better resources.

I also think it's a valid criticism to note that the comparison to btrfs promised in the video's introduction was pretty much nonexistent.
As far as the parity thing, yeah the graphic is an incorrect oversimplification.
He actually uses a number of graphics (all from different sources AFAIK; they aren't original to him) that say the same thing. He himself is speaking very generally and doesn't get to that level of detail in any way. But it seems I've run across a number of people here in the not-too-distant past who believe that RAIDZ1 has one dedicated parity disk, RAIDZ2 has two, etc. I was a little puzzled about why they would think that, but when I see the graphics Wendell is using, I think the question is answered.
 

NickF

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I think it's a valid criticism. As interesting as the video and the history are, I don't think they're going to be especially helpful for a n00b who's trying to set up a sensible ZFS pool....And I think (based both on the text Bikerchris wrote, and the place he posted it) that's how he intended it to be used (regardless of what Wendell may have intended). For that purpose, I think there are other resources that would be more helpful (many of which are already posted here). If you want an overview of the history of ZFS and what it's designed to accomplish, great. If you want to understand how to make it work for you, there are probably better resources.

I do agree with you, the video doesn't give the viewer much in the way of helpful information on how to use ZFS. However, I think it was rather obvious that that wasn't the goal of the video at all. He starts the video by stating that it's intended purpose is to teach people what ZFS is. There is a subtle distinction there, but they are indeed two different topics. Just because his actual goal was different than your expectation, doesn't mean its not worth utilizing as a resource when learning what ZFS is...

However, Wendell's marketing here might be a little off. He posted this on Level1 Linux, not Level1 Enterprise where it should have been. If you listened to the whole video, you will notice he uses multiple comparisons to NetAPP and hardware raid, as well as draws the warm and fuzzies from people familiar with the Sun of old. Really, he is speaking directly to those SysAdmins out there who have no idea what ZFS is and is telling them why the really should be using it.

I also think it's a valid criticism to note that the comparison to btrfs promised in the video's introduction was pretty much nonexistent.
To go along with my above statement, let's think about the enterprise. Rightfully or not, btrfs has a bad reputation with folks who's job it is to maintain systems in the enterprise. Whether at this point btrfs is ready for that model or not, when it was supposedly "stable" and RAID5 didn't work...People looked away and haven't come back. Wendell sums up that sentimate and seems to largely agree with alot of those who hold that opinion. He mentions btrfs as something which is a possible alternative, and states why he feels ZFS is a better choice, just like he does with NetApp and hardware RAID. I think that is good enough for the goal of his video.

He actually uses a number of graphics (all from different sources AFAIK; they aren't original to him) that say the same thing. He himself is speaking very generally and doesn't get to that level of detail in any way. But it seems I've run across a number of people here in the not-too-distant past who believe that RAIDZ1 has one dedicated parity disk, RAIDZ2 has two, etc. I was a little puzzled about why they would think that, but when I see the graphics Wendell is using, I think the question is answered.
But again, think about it from the lens of someone who knows nothing about how ZFS, but is a sys admin in charge of a large organization. When you are managing dozens or hundreds of sites and you want to know what your options are for storage, while juggling all of your other 10,000 responsibilities, how deep down the rabbit hole are you going to go? I don't really think the distinction between having 2 dedicated parity drives or having 2 drives worth of parity being stored over all of the disks in the vdev really matters to them.

I just think you are being critical for the sake of zealotry. This was a great piece of information worth sharing. He just marketed it wrong--and that is forgivable. He's a systems engineer not a marketing specialist.
 
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We at the Level1Techs community do not view this as trollish or zealtry behavior and just valid basic criticism. Mods please do as you will, thank you.
 

NickF

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We at the Level1Techs community do not view this as trollish or zealtry behavior and just valid basic criticism. Mods please do as you will, thank you.
To be very clear I am speaking for no one but myself, nor have I ever claimed to. I also am not affiliated with Level1 in any capacity.
That being said, I have no idea who authorized you to speak for an entire community of people or why you thought it prudent to post in this thread to state that you were.

On the topic at hand, while I have made it known as to what my opinions are about the above criticism of this video, I feel I must add one additional comment at this point.

A wise man once told me: Information Technology is about seeing the forest through the trees. I know this community is focused on the "tree" that is FreeNAS/TrueNAS. That being said, I feel alot of us often forget there is a wide forrest full of other "trees" that are seasoned system admins who have no idea what ZFS is. If we constantly nitpick on community members who are contributing to spreading the ZFS knowledge base, we were going to get no where fast.
 

danb35

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I just think you are being critical for the sake of zealotry.
It's amusing that you write this after spending several paragraphs making my point for me. I suggest that you don't understand my point (despite my having stated it explicitly), which points to you defending the video against criticism I haven't made "for the sake of zealotry." I said:
As interesting as the video and the history are, I don't think they're going to be especially helpful for a n00b who's trying to set up a sensible ZFS pool. And I think (based both on the text Bikerchris wrote, and the place he posted it) that's how he intended it to be used (regardless of what Wendell may have intended).
And if you actually pay attention to the thread, you'll notice that the OP has conceded this point. It may be interesting to a lot of people, it may be useful to a lot of people, but enterprise sysadmins really didn't seem to be in view of the OP.

And why you felt the need to bring up my response in a post in their forum is completely beyond me.
 
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