Growing pool with mismatched vdev. How to plan?

[Keven]

Hi,

I have currently 4X4TB in RAIDZ1 and I'm slowly starting to outgrow the space. For the future I was planning to add another vdev to the pool and I would like to get at least 8tb drives, but for 8tb drive it start to be too big for my like with just 1 drive of redundancy. As mentioned on this forum as the drive get more TB the chance of a second drive failing increase.

So to keep at least 75% of space efficiency I thought of buying 8x8TB drives in RAIDZ2 which would max out nicely my case while leaving 2 5.25inch Bay so I can out hdd for replacing a failing drive

So basically my initial plan was to add a 8 drive vdev to my pool which have already 4 drives vdev... Is it possible I might have misread some post about being able to mismatch vdev, I'm not sure.

My GOAL is having a single SMB share which reference the 4x4tb and 8x8tb it would be ok to have separated pool if absolutely needed.

This NAS main uses is for a plex server over a 1 gigabit connection so for the performance its already maxing out the Lan. I know that with mismatched vdev it can affect performance a little bit. But I don't think I will see a difference for my use case.

 

[CompuGlobalHyperMegaNet]

By adding the 8x8TB RAIDz2 vdev to the same pool as the 4x4TB RAIDz1 vdev, you'll still only have 1 drive worth of redundancy(!).

Your pool is only as resilient to failure as it's least resilient vdev. If 1 parity disk isn't enough redundancy for you with 8TB (and IMHO it probably shouldn't be), then what I'd do in your situation is add the new 8x8TB to a new pool. If you want just a single pool, then you could take it a step further by replicating the 4x4TB based pool to the new 8x8TB based pool. Migrate your plex server, mount points, jails etc. to the new pool. Remove the old pool and then add the 4x4TB disks to the new pool as another RAIDz2 vdev.

You'll lose 4TB~ of capacity but you'll gain the peace of mind that any two disks can fail without losing data.

 

[jgreco]

Hi,

I have currently 4X4TB in RAIDZ1 and I'm slowly starting to outgrow the space. For the future I was planning to add another vdev to the pool and I would like to get at least 8tb drives, but for 8tb drive it start to be too big for my like with just 1 drive of redundancy. As mentioned on this forum as the drive get more TB the chance of a second drive failing increase.

So to keep at least 75% of space efficiency I thought of buying 8x8TB drives in RAIDZ2 which would max out nicely my case while leaving 2 5.25inch Bay so I can out hdd for replacing a failing drive

So basically my initial plan was to add a 8 drive vdev to my pool which have already 4 drives vdev... Is it possible I might have misread some post about being able to mismatch vdev, I'm not sure.

My GOAL is having a single SMB share which reference the 4x4tb and 8x8tb it would be ok to have separated pool if absolutely needed.

This NAS main uses is for a plex server over a 1 gigabit connection so for the performance its already maxing out the Lan. I know that with mismatched vdev it can affect performance a little bit. But I don't think I will see a difference for my use case.

Alternative strategy:

Create a new pool with the 8x8TB drives in RAIDZ2.

Copy all the data to the new RAIDZ2.

Destroy the old pool.

Add the old 4x4TB drives to the new pool as a RAIDZ2.

*done*

 

[Keven]

By adding the 8x8TB RAIDz2 vdev to the same pool as the 4x4TB RAIDz1 vdev, you'll still only have 1 drive worth of redundancy(!).

i know, i was fine with 4x4TB RAIDz1, it's not too long to rebuilt 4TB, however rebuilding 8TB is longer so the time of vulnerability is roughly double and you have double the number of disk so basically double the chance of a second drive failing and that's where i draw the line for the safety of the data. it's mainely my blu-ray collection that i have on there so if my 4x4TB array would have failed before i would just re-rip my blu-ray

and as far as i know if 1 of the 8TB drive would fail, it would not tax the 4x4TB vdev when resilvering? so even if 1 vdev has 1 drive redundant and the other vdev has 2 the overall odd are pretty much the same for each vdev in my opinion.


and just to know because the gui is not user friendly when doing things not 100% best practice if i tried to simulated adding another vdev to my pool it's not letting me choose anything other than Raid-z. is it possible to choose raid-z2 in the gui or it's CLI only?

also as mention my main goal is not necessarily 1 pool, but ultimately 1 SMB share that would reference all my storage and both of you didn't address it (maybe because it's not possible... i don't know so if you could enlighten me on that topic).

thanks
Keven