Upgrading A Vdev Size?

[modi]

I have a few vdevs all of 2 drives in mirror. So 1+1, 1+1, 1+1, 1+1.
They are currently all 4TB 4k SAS3 Drives. I've ran out of storage space and physical room for new drives, and don't have the funds to grab a new chassis at the moment.

What I was planning on doing is ordering 2x 8TB 4k SAS drives to use.
My question is, is it 100% safe to turn off, remove drive 1 in vdev 1, turn it back on, let it resilver, then turn it back off, and remove drive 2 in vdev 1, turn back on and let it resilver from the new drive 1.
I should then havs 3 vdevs of 4tb drives, then 1vdev of 8tb drives, and have more storage space available on that pool correct?

Furthermore, there is no real way my pool can be screwed up correct? Because I can always pop in the old drives and all my data is back.
And are there any other considerations?

 

[sretalla]

My question is, is it 100% safe to turn off, remove drive 1 in vdev 1, turn it back on, let it resilver, then turn it back off, and remove drive 2 in vdev 1, turn back on and let it resilver from the new drive 1.

Yes... maybe not 100% but pretty close to that. (you can never account for powering up and down as a trigger for drive failure, so that's the o.00001%)

I should then havs 3 vdevs of 4tb drives, then 1vdev of 8tb drives, and have more storage space available on that pool correct?

Yes

Furthermore, there is no real way my pool can be screwed up correct? Because I can always pop in the old drives and all my data is back.

Not sure that's 100% either, but if you're methodical and don't move more than one step at a time, it should be a robust process.

 

[modi]

For your last quote, yeah not 100% really obviously things happen. But my point being I can always throw the 2 old drives back in and my pool will be restored anyways.
But sounds like this should work. Just wanted to ensure everything I've read I've understood correctly, before I drop $250 on new drives.

Do you happen to have any experience with calculating usable storage space with mismatched size drives? Was just curious how much extra I should gain from this.
I will go from 4x Vdevs of 2x (mirror) 4tb drives each, to 3x vdevs of 2x 4tb drives+1 vdev of 2x 8tb drives.
I think I currently have like 13tb total usable space.
It seems like I'd get a +4tb increase of usable space? Seeing I was already using 4tb out of the 8tb after resilver. If that makes sense.

I'm hitting the 80% capacity currently which is why I'm doing this lol
Thanks.

 

[sretalla]

VDEVs are striped together in a pool, so the capacity of all the VDEVs summed up is the total pool capacity. Your calculations seem reasonable in that sense.

But my point being I can always throw the 2 old drives back in and my pool will be restored anyways.

No. Don't make that assumption at all.

Each disk that is resilvered into the pool becomes known in metadata stored on other disks in the pool, so bringing back an old one (even if it still has more-or-less the same contents) isn't a magic fix to put the pool back as before... the gptid of member disks won't be the same.

As I said, be careful and methodical about doing only one step at a time so that you can recover at each step if needed (by replacing/resilvering the right disk in the right place).

 

[modi]

Thank you for thr clarification