Need help on understanding

[RandomLegend]

Hello Community!

i need some help understanding something. I searched and went through multiple posts here but i am not sure if i understood correctly.

Right now my TrueNAS Core has 2x 8TB Drives in it that run in "Mirror". Now i am running out of space on those disks and want to get a third 8TB drive... Can i "simply" upgrade the "Mirror" zo "Raid-Z1" without any data-loss?

Thanks in advance!

 

[Patrick M. Hausen]

No, you cannot. You need to create a completely new pool from 3 disks to change the topology from mirror to RAIDZ1.

See the ZFS primer for reference:

ZFS Primer

Background information about the Zettabyte File System (ZFS).

www.truenas.com

 

[RandomLegend]

Would i have to save the files somewhere in between? Or can i do this without losing the data that's already on that drive?

 

[Patrick M. Hausen]

You will need to save the data.

Alternatively you can add two more disks in another mirror vdev doubling your available space. Adding vdevs is always possible. Changing the topology of an existing vdev from/to one of the RAIDZn level is what is not possible.

 

[RandomLegend]

Darnit...thats very very unfortunate...my NAS is the biggest storage i have so i simply cannot save the files somehwere else. I don't want to add another mirror because i wanted to go with RAID-Z1 with a total of 5 disks in the future to maximise space...

I now assume that if i were to create a pool consisting of 3 drives in a Raid-Z1 that i could NOT add new disks in the future to that aswell right? So whatever i create NOW with the Disks i have now, will have to stay as it is. Right?

 

[Patrick M. Hausen]

I now assume that if i were to create a pool consisting of 3 drives in a Raid-Z1 that i could NOT add new disks in the future to that aswell right? So whatever i create NOW with the Disks i have now, will have to stay as it is. Right?

Spot on. You cannot add disks to a RAIDZn vdev. You could add another 3 disks in another RAIDZ1 vdev to double your capacity like with the mirrors.

 

[RandomLegend]

Alright...but then i'd have to buy them all at once :-D My plan was to add them as i please...

But when i do they will be added to the pool, correct? That means the datasets on the pool can simply use the new space that became available, correct? In my case, there is my plex library sitting on my current 2x8TB Mirror. If i buy 3 new drives, make a raid-z1 add them to that pool, my plex would now see ~24TB of space instead of the 8TB right now. Right? I don't have to create a new dataset on those new drives and tell Plex to look at this dataset aswell.

 

[Patrick M. Hausen]

Again, correct. But making a pool from different topology vdevs is generally discouraged. Nothing bad will happen to the data but you might experience odd and inexplainable performance scenarios.

 

[RandomLegend]

Thank you so much!

But mixing same topologies but with different sizes would be okay? So i could go for 2x16TB instead, do a mirror and add it to the pool..That would be fine?

 

[Patrick M. Hausen]

That would definitely be better. I read you have space for five disks? Then if in the future you ever want to replace the 8 T with new 16 T drives, you can do that live and while keeping full redundancy. I'd look for the sweet spot in price per capacity - sometimes 14 T is cheaper than 16 etc.

 

[RandomLegend]

i didn't even know there are 14TB drives lol. Thanks!

How would i do that? [...] you can do that live and while keeping full redundancy

After this conversation my plans will be to get two new drives; 2x16TB (or 14TB). So then i would have 2x8TB (mirror) and 2x16TB (mirror). Let's say my space is used up 80%....how could i achieve to replace the 8TBs with new 16TBs without losing data? oO

 

[Patrick M. Hausen]

Insert new 14 or 16 T disk in the available slot. Perform replace operation for one of your 8 T drives. That's available in the UI. When finished, remove that 8 T drive, insert second larger one. Perform replacement. Remove last 8 T drive. Done.

 

[RandomLegend]

Ah utilizing the 5th unused slot...yeah i'm tired and didn't think of that.

Thanks again! I know now what to do in the future