Hot spare for a 3-way mirror, is this looks right?

[Shigure]

My TrueNAS Scale is finally up and running. I have a 5-wide RaidZ2 data vdev with a 3-way mirror SSD metatdata vdev for my storage pool. When I asked about my setup before, from the suggestions I chose the 3-way mirror + 1 hot spare.

Now I have the pool up and running, but when adding hot spare to the pool, I can only add a spare vdev instead of assigning a spare SSD for that 3-way mirror vdev only. Here's the screenshot.

Is this looks correct?
If everything is correct, any of the SSDs in the metadata vdev failed the spare should kickin. If any of the HDDs in the data vdev failed nothing should happen?

 

[sretalla]

A couple of points on that...

It's great that you have understood that the Metadata VDEV is pool integral and thus important to ensure it doesn't die.

How you've arrived at the decision to go for both a SPARE and 3-way mirror is a little puzzling.

I would expect that a 3-way mirror is enough to cover you for loss in even the most extreme case where you lose 2 of the 3 mirrored SSDs, allowing you some time to replace one or both of them before losing the pool.

Are you concerned about having a very long lead-time to get to the box in the case of a failure?

If you're really wanting the best protection for your pool with those drives, just make it a 4-way mirror, forget the spare idea.

 

[Shigure]

A couple of points on that...

It's great that you have understood that the Metadata VDEV is pool integral and thus important to ensure it doesn't die.

How you've arrived at the decision to go for both a SPARE and 3-way mirror is a little puzzling.

I would expect that a 3-way mirror is enough to cover you for loss in even the most extreme case where you lose 2 of the 3 mirrored SSDs, allowing you some time to replace one or both of them before losing the pool.

Are you concerned about having a very long lead-time to get to the box in the case of a failure?

If you're really wanting the best protection for your pool with those drives, just make it a 4-way mirror, forget the spare idea.

I understand it's kinda weird to have that hot spare setup given that I already have a 3 way mirror. I cannot guarantee if I always have access to that box within a day(need travel sometimes) so I want to make sure if a drive dies everything will still be fine. Additionally I already have those 4 SSDs in the box but they are not all new drives, the one for hot a new one without any wearing while they other 3 all have some but not a lot wears on them. I didn't expect them to die at the same time though.

Without my situation, did I understand how hot spare work in a mixed pool with SSD and HDD? For a pure HDD pool as long as I have a hotspare equal or larger than the max capacity of any single drive I should be good(if my understanding is correct).