Hello community!
my past “Me” was quite stupid and created a mixed vdev striped mirror. I have 2x8TB and 2x18TB in a mixed pool.
I now got myself two new 18TB plates and want to swap out my current 8tb plates with those.
I searched far and wide and went through some forum posts but i am not quite 100% sure so i also send out a deep-research agent on the matter.
Do i have to copy all my content to an external NAS, completely wipe the pool, swap out the plates and copy all the files back onto it?
Or can i really just plug in one of the new 18TB plates (i have one SATA port free), click on Replace Disk on the 8TB Mirror, replace that with the 18TB, wait for resilver and repeat the process for the other 8TB plate? That way i wouldn’t have to copy away all the files and still get my final 4x18TB
Can someone enlighten me?
Thank you very much!
You need to be accurate with the terms.
Do you have a pool made up of 2 vdevs? Is each vdev a 2-way mirror of 2x8TB and 2x18TB?
If that’s your setup, you can replace each 8TB drive with an 18TB drive without starting over. Then use the “Expand” option to grow the size of your pool, which will be 10TB larger.
If you have enough SATA ports, it’s preferable to “Extend” the mirror vdev into a 3-way or 4-way mirror, and then remove the 8TB drives from the mirror vdev. This will allow you to keep redundancy at all times.
Sorry if i mixed up the terms here.
This is what my pool looks like:
Additionally i have one SSD which is the boot drive for TrueNAS itself.
I have one last SATA port open so i can plug in one additional drive. So extending the mirror by both new 18TB drives is no option i assume.
One at a time.
Convert the 2-way mirror of 8TB drives into a 3-way mirror by attaching an 18TB drive. Then after it finishes, convert it back into a 2-way mirror by removing one of the 8TB drives. Then repeat again until you finish with a 2-way mirror of 18TB drives.
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First of all:
Thanks for the quick answers!
Sorry i’m confused now 
So NOT Replacing the 8TB disks with the 18TB disks and later “expanding” the whole pool?
But instead do this?
How many SATA ports do you have to work with at the same time? We usually recommend ‘in place’ replacements by adding the additional drive(s) and choosing replacements with everything online.
If you don’t have enough SATA ports, you end up taking a 8TB off line, powering down, installing the 16TB in it’s place and completing a drive replacement.
Mirror VDEVs are a bit more flexable as you could take the 2 wide, 8TB and add the 2x, 16TB as additional mirrors in that VDEV, make sure resilvering completes, then remove the 2x 8TB drives from that VDEV. Then you would probably need to EXPAND that VDEV to get the space from 8TB mirror to 16TB mirror. Screenshot showing EXPAND button on right side once you select the older VDEV.
I have 6 SATA Ports.
1 - Boot SSD
2 - 8TB
3 - 8TB
4 - 18TB
5 - 18TB
6 - One-By-One-Replacement Plate
Could i “simply” plug in one 18TB plate, click on one of the 8TB Plate and click on Replace, select the 18TB, wait for resilver, take out that 8TB plate, plug in the other 18TB and repeat for the remaining 8TB?
Yes. Don’t forget the EXPAND at the very end to get all the space
Got it, thank you so much guys!
Just wanted to make sure it’s safe to do before nuking my pool lol
I don’t have access to my PC. I was trying to avoid the confusion. TrueNAS UI uses confusing terms that do not match native ZFS terminology.
You need to “Extend” a vdev in the UI. In ZFS this is known as “attach”.
It worked flawless, thank you people!
