Slideshow explaining VDev, zpool, ZIL and L2ARC for noobs!

[Stephens]

Regarding slide 27, if I'm reading and calculating correctly, 'n' doesn't represent the number of drives of usable space desired. I think 2^n does. I don't know how to reword it. In the examples given, 'n' is an to an index that increases from 1 to whatever such that

Code:

1 - 2^1+1=2+1=3    2^1+2=2+2=4
2 - 2^2+1=4+1=5    2^2+2=4+2=6
3 - 2^3+1=8+1=9    2^3+2=8+2=10
4 - 2^4+1=16+1=17  2^4+2=16+2=18
5 - 2^5+1=32+1=33  2^5+2=32+2=34
6 - 2^6+1=64+1=65  2^6+2=64+2=66

If I, for instance, want 4 usable drives (my current setup), N = 2. 2^N would be 4, then 2 for parity (zraid2) = 6 drives. I did try to figure out the formula for deriving "n" based on number of desired drives, but I gave up. The inverse of an y-eponential is a y-root, but I couldn't finish it out. The best I could come up with is to use the table your formula builds (though 'n' would be an index, not number of desired usable drives). Your usable drives desired needs to be a number after the first equal sign, and your "n" becomes whatever "n" is on the same line.

Sorry I couldn't be more constructive on how to modify it, but I did at least want to point it out.

 

[cyberjock]

I know what you mean, but I expect the administrator to understand the theory and be able to calculate backwards for his total available disk space. If he can't do that he shouldn't be administering a FreeNAS server. There are limitations to how much I can teach someone on a slideshow. If the reader can't understand it there's not much I can do to help him understand. If I gave the slideshow to my mom she wouldn't understand any of it.

 

[Stephens]

Understood. Most people will get it. It's just that "N" isn't what it's described as. Unfortunately, not everyone setting up FreeNAS, reading this thread, or watching the slideshow will be an "IT Administrator" type. Anyway, at least a noob reading the thread will be cautioned about "N" since my post is here. That might at least cut down on their momentary confusion when trying to learn this stuff.

Thanks again for the slideshow. It has already shaped how I do things going forward.

 

[cyberjock]

I decided to look at the whole "N" issue again. You are 100% correct Stephens. I've changed the slide. I would try to say I was drunk or something but since I don't drink I have no good excuse for why I said that before. I was just plain wrong. :P

Anyway, I added another comment to "RTFM" on slide 26 or 27(forget which). Hopefully we can hold back the swath of people that don't read the manual. In the last 3 days I think i've seen 5 threads asking questions that were blatantly answered in the manual. The one that comes to mind was someone asking about changing the MTU to 9000 through reboots. The manual actually gives an example for changing a NIC setting for the MTU to 9000. It becomes pretty obvious sometimes that people either didn't use or didn't read the manual. I did my first 2 builds on my own with only the manual and the only issue I had was a hardware compatibility issue, so I have high praises for the manual. Before FreeNAS I had only heard of FreeBSD and never actually used or seen it.

Anyway, guides are updated. :)

 

[ProtoSD]

noobsauce80,

I can completely understand your frustration with people that don't RTFM, or the FAQ or anything and just pop in here like they deserve some type of chauffeur for FreeNAS. I'm sure you've seen me snap a few times. No matter how much effort you put into your slideshow, there'll always be more than handful of those people that are just clueless or something. I'm really glad you made your slideshow and are trying to do your best to make it the best. Huge Thanks!

 

[cyberjock]

It's really disappointing to see people that don't RTFM. Especially ones that aren't familiar with FreeBSD or ZFS. They'll ultimately lose data and come crying in the forum asking for someone to magically save them. It sucks having to tell someone they really did lose everything and there's no way to fix it.

I've seen you snap and I'm shocked you've maintained your composure. Several times I wish I could just put "RTFM" and close the thread. I wouldn't really do that to someone, but at some point they have to learn for themselves. Maybe I should start teaching a course in FreeNAS or something. :P Maybe there's money in it. I got lots of time since I'm unemployed.

I started using FreeNAS in Feb/March time frame and I had nobody to ask questions to and I had a system up and running within hours. I normally ignore the manuals, but the FreeNAS manual is extremely well written. It gave me all of the information I needed to be up and running.

 

[bfishernc]

Nicely done. As a new user, it's nice to see this information as it summarizes and confirms everything read elsewhere. Thanks for the hard work.

 

[bkoo]

This is immensely helpful presentation! Great work!

I have one question though.
It says "VDevs cannot be removed from a zpool after they have been added."
OK, I can understand that. Then, is it possible to replace hard disks in a vdev in a zpool with larger disks?

Let's say I have set up my zpool as follows:
vdev1: (2) 2 Tb HDDs (mirror)
vdev2: (2) 1 Tb HDDs (mirror)
Total: 3 Tb

(Btw, the FreeNAS manual explicitly says,
"you can stripe a new vdev (and its disks) with the same type of existing vdev in order to increase the overall size of the ZFS pool... Highlight the required number of additional disk(s), select the same type of RAID used on the existing volume, and click Add Volume."
http://doc.freenas.org/index.php/Volumes#Using_Volume_Manager_After_a_Volume_Has_Been_Created
Is the manual outdated?)

Can I expand this zpool by replacing all the HDDs in vdev2 with larger ones?
vdev1: (2) 2 Tb HDDs (mirror)
vdev2: (2) 2 Tb HDDs (mirror)
Total: 4 Tb

I'm confused because I'm not sure if you can expand your vdev without first removing it from a zpool.

Thanks for your answer in advance.

 

[Stephens]

Does the presentation say something that conflicts with the manual? The presentation also says you can grow ZPOOLs by adding VDEVS (slide 6). It just warns if you lose 1 vdev, you loose the whole ZPOOL.

You don't remove the vdev from the pool. You use the GUI to notify FreeNAS you're removing a drive. Then you shut down, take out the drive, put in a new one, then notify FreeNAS of the replacement (use the procedure documented in the manual).

 

[bkoo]

Thanks for the answer!
So that way I can grow my existing pool, replacing old drives with bigger ones.

As for the manual, it's just that the manual says the new vdev you are adding to your zpool should be "the same type" of the existing vdev (w/ same RAID), but the presentation says you can mix different types of vdevs in a zpool.
That might need a clarification...

 

[cyberjock]

Normally, if you created a vdev that is RAIDZ2, you would WANT to create another RAIDZ2 vdev instead of say a RAID0. Why would you create a RAIDZ2 and then add a RAIDZ0 effectively giving up redundancy of the zpool for the second vdev? The presentation says that you CAN mix types because it IS acceptable to create a RAIDZ2 and RAID0 in the same zpool. It is a valid and acceptable configuration, but it is not recommended because you lose redundancy. The purpose of the example was to show that as the administrator you CAN choose settings that remove redundancy that you thought you had. Several people have added a RAID0 to a RAIDZ2 and then wondered why they lost all of their data when a drive in the RAID0 failed. This is to show that FreeNAS WILL let you do things that any sane administrator would never do.

 

[Saeed A Siddiki]

thank u note

AMnoobsauce80, your like the YODA in this! i just read your slides and watched it with real NEWBIE enthusiasm! i think for all those new-folk to FREENAS 8 (like myself!) one has to read it in the PPT format a a few times and start drawing mind maps! I am attaching a HUGE mind map which may help more people! just thinking outloud here with everyone else in a visual PDF-ing way
thanks AGAIN AMnoobsauce80

 

[cyberjock]

AMnoobsauce80, your like the YODA in this! i just read your slides and watched it with real NEWBIE enthusiasm! i think for all those new-folk to FREENAS 8 (like myself!) one has to read it in the PPT format a a few times and start drawing mind maps! I am attaching a HUGE mind map which may help more people! just thinking outloud here with everyone else in a visual PDF-ing way
thanks AGAIN AMnoobsauce80 View attachment 1332

That thing shrunk down to nothing thanks to the forum. Can you provide a link to me in PM to download that file? I'll see about hosting itfor others that may be interested.

 

[Saeed A Siddiki]

OOOH OOOPS -- just uploaded it to Dropbbox - keep it coming mate!

https://www.dropbox.com/s/i05hit7jhf7b8bo/FREENAS Directory and Permissions setup .jpeg

 

[cyberjock]

I've downloaded the file. I'll be adding your picture a little later today to my dropbox and adding the link to the 1st post. If you want you can remove your link if you are concerned with oversharing your Dropbox account.

 

[Saeed A Siddiki]

http://dl.dropbox.com/u/4424791/FREENAS Directory and Permissions setup .jpeg

hey guys here is another updated version of my drawing for anyone interested in visual FREENAS representation and too much workflow -- cheers

 

[Saeed A Siddiki]

no worries man - its in the public domain anyways - thanks again! really excited today will be the rebuild day! if that supemicro controller shows up!

 

[cyberjock]

Updated the guide to reflect FreeNAS 8.3.0. Please post any issues found.

Thanks.

 

[bollar]

Updated the guide to reflect FreeNAS 8.3.0. Please post any issues found.

Thank you for this presentation. It's does a great job clarifying this stuff!

 

[Yell]

Great GUI (reading the PDF versions)

if you have time change the following:

Page 4: add short description for Raidz (like you did with 0 and Mirror) something like "Strip + Parity", "Strip + 2xParity"

Page 17: Replacing disk, add a "swapoff -a" from the command line, else swap will block the device. You will need a reboot for attaching a harddisk to the port of the failed.
(http://support.freenas.org/ticket/493)