Extending a RaidZ2 questions.

[3l3t]

I'm working to extend a Volume that is using RAIDZ2, on a FreeNAS 11.1 system.

In my test environment I receive the error "You are trying to add a virtual device consisting of 4 device(s) in a pool that has a virtual device consisting of 6 device(s)" If I add 6 new devices it expands the volume just fine.

Do I have to add the same number of disks that exists on the old pool?
If yes, how do I find the number of disk being used by the pool on my production machine?

 

[Chris Moore]

Do I have to add the same number of disks that exists on the old pool?

It sounds like you need to review some of the introductory material. I am going to give you some links that you really need to read and save and review as needed. Don't feel like you can't keep asking questions though. Long story short, in a ZFS storage pool, all the vdevs (virtual devices) should be the same RAIDz redundancy factor (RAIDz2 for example) and they should all be the same number of drives. So, if you have a pool that starts with six disks, you would expand it with another six disks.
I made a video to help: https://www.youtube.com/watch?v=Pb9H236V-l0

Here are some links to help you understand the technology and terminology:

Did you read the manual? There really is a lot of useful information there:
http://doc.freenas.org/11/freenas.html

Updated Forum Rules 4/11/17, important to know:
https://forums.freenas.org/index.php?threads/updated-forum-rules-4-11-17.45124/

Slideshow explaining VDev, zpool, ZIL and L2ARC
https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

Terminology and Abbreviations Primer
https://forums.freenas.org/index.php?threads/terminology-and-abbreviations-primer.28174/

Why not to use RAID-5 or RAIDz1
https://www.zdnet.com/article/why-raid-5-stops-working-in-2009/

 

[kdragon75]

Take a step back. It's easy to do irreparable damage to a pool if you get any of this wrong. You need to fully understand how disks, vdevs, and pool all work before you do anything with testing let alone a production machine.
The infamous Cyberjock has a decent write up explaining some of this.
https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

There are also some good links and info in the official docs
http://doc.freenas.org/11/zfsprimer.html

 

[3l3t]

Thanks Chris. I've inherited this system from another sysadmin.

 

[danb35]

...and, as a big-picture thing: you can't turn a six-disk RAIDZ2 into a ten-disk RAIDZ2 (yet). You can add a second vdev to the pool, though in that case it's recommended that the vdevs match.

 

[NasKar]

...and, as a big-picture thing: you can't turn a six-disk RAIDZ2 into a ten-disk RAIDZ2 (yet). You can add a second vdev to the pool, though in that case it's recommended that the vdevs match.

I've read the Cyberjock's write up on pools, vdevs etc and he makes that point that the a second vdev to the pool should match the RAIDZ2 and number of disks but could you explain why that matters. BTW way I"m following that recommendation.

 

[danb35]

a second vdev to the pool should match the RAIDZ2 and number of disks but could you explain why that matters.

I bolded the operative word here--it's "should", not "must." It's best for performance if the vdevs match--same RAIDZ level, same number of disks, same capacity, same (or similar) performance characteristics. But it certainly isn't mandatory.

 

[Stux]

Main thing is if you decide later you really did want to add a 6 disk vdev, you can’t fix it with out destroying and rebuilding the pool.

 

[danb35]

you can’t fix it with out destroying and rebuilding the pool.

...until FreeNAS 12 is released (probably).

 

[gpsguy]

One way is to run zpool status

If yes, how do I find the number of disk being used by the pool on my production machine?

 

[Chris Moore]

I've read the Cyberjock's write up on pools

The document @cyberjock made is very good, which is why it is still cited as a reference, but there have been a few changes over the years that are not accounted for. There has been discussion of making an updated version, but it takes time and there is often not enough.