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.

  • Zimmie
    2•7 days ago

    @SexualPolytope Unfortunately, that’s not possible. When you add a special device, all metadata (which is to say the filesystem tree itself) is written only to the special device.

    This *can be okay*, as long as you have a good backup strategy. I would be comfortable using a single special device for a desktop which I back up to some other pool, for example.