I currently have a zfs pool with mirrored vdevs, and it’s working well. It only has HDDs. I was planning to add an SSD I have lying around as a Metadata Special Device, since I’ve read that it can improve performance by quite a bit. I’ve also read that if I do that, and if the special device dies, I lose my pool.

Now, I don’t want to buy new SSD pairs for mirroring this one, so is there a way to ensure that the metadata is also stored on the HDD as usual, along with the SSD? I guess I want it to work like a cache for the metadata, and not the only place for it.