Questions about how Unraid handles ZFS with vdevs, pools (6.12 rc7)

[yoleska]

As I embark upon this new road with Unraid and ZFS, my knowledge is a bit scattered, and I'm looking for direction.  Please excuse the ignorance here, I'm a noob to Unraid, but my career is in networking and security.  I can follow directions well.  

 

I have general understanding of how ZFS is structured:  A pool consisting of vdevs which contain n number of disks.  

 

But as I just noticed when I setup my first ZFS pool there was no mention of creating a vdev in any of the settings.  So when I bring my new disks online (4x 16TB), I want to add them to the pool as a second vdev, but I'm not sure how to do this.  Like how do I let Unraid know those disks are the second vdev of the original pool.

 

And then let's imagine that they are part of the ZFS pool (I find out how to have 2 vdevs in 1 pool), I have a question about shares and file system use in general.  If I create a share, I would assume that it would just use both vdevs and share the load between them.  Is that the case with Unraid or am I missing something?  I definitely don't want 2 pools and then have to have my /appdata or /coolmemes shares split between them.  I want Unraid to think of all 8 disks as an entire pool that I can address with data structures.  

 

 

[JorgeB]

28 minutes ago, yoleska said:

there was no mention of creating a vdev in any of the settings.

You can see/choose that by clicking on the first pool device at pool creation.

29 minutes ago, yoleska said:

So when I bring my new disks online (4x 16TB), I want to add them to the pool as a second vdev, but I'm not sure how to do this.

Stop array,  add all 4 devices to pool, start array, note the the new vdev has to be the same width as the exiting one(s), and due to a bug, at the moment you cannot add a vdev made of smaller drives, so make sure you start with the smaller ones if they are different capacity. 

 

32 minutes ago, yoleska said:

If I create a share, I would assume that it would just use both vdevs and share the load between them.

Correct. 

[yoleska]

Oh yeah, I will blow this test zpool out of the water and get the 4x16TB added as primary and then add the smaller vdev to the pool.  Thanks...next question.   

[JorgeB]

1 hour ago, yoleska said:

and get the 4x16TB added as primary and then add the smaller vdev to the pool.

Just to confirm, smaller capacity vdev needs to be first.

[Tun2022]

Hello,

 

I would like to create a one pool for all these drives using 6.12 rc8.  How do I do this in GUI or maybe in command line?

 

Thanks

 

5x3TB

9x4TB 

 

Thinking:

1) Using GUI to create a pool tank 5x3TB raidz

2) Using command line to add

       zpool add tank raidz /dev/sdra1 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1  (assume first 5x4TB)

        zpool add tank raidz /dev/sdrf1 /dev/sdg1 /dev/sdh1 /dev/sdi1  (assume last 4x4TB)

 

Will this work? - any suggestions appreciated.

 

[itimpi]

I do not think you can do what you want in one pool.   All vdevs in a given pool have to have the same number of drives 

[JorgeB]

10 minutes ago, itimpi said:

All vdevs in a given pool have to have the same number of drives

Correct, you can start with 5 x 3TB, then add another vdev made of 5 x 4TB, and you can do that using the GUI, if you can get an extra 4TB drive you can then add another 5 x 4TB vdev.

[Vr2Io]

I try move a btrfs RAID0 pool to zfs raidz x2 pool in this way.

 

6x 12TB and 6x 14TB

 

One big difference observed vs btrfs pool, let say when filling over 144TB data (12x12TB), then data will sit on six 14TB. But zpool will stripe in weight to all 12 disks, (because both vdev in different capacity), as result seems will always use 12 disks.

 

But this only valid when pool was created before filling data, not for expansion vdev later on.

 

 

Edited June 14, 2023 by Vr2Io

[doubley]

On 6/10/2023 at 2:26 AM, JorgeB said:

 

Stop array,  add all 4 devices to pool, start array, note the the new vdev has to be the same width as the exiting one(s), and due to a bug, at the moment you cannot add a

Hi Jorge, do you know if this has been fixed as of the latest, 6.12.1? I've been having issues added a vdev of a smaller capacity to my zpool, unsure if due to user error or this bug still existing.

[JorgeB]

6 hours ago, doubley said:

Hi Jorge, do you know if this has been fixed as of the latest, 6.12.1?

No yet, you still cannot add a vdev made of smaller devices than the current one.