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ZFS is an opensource COW filesystem used by enterprise and serious homelabbers for it's data safety and extensive feature set.

OpenZFS is the active branch now developed primarily for Linux with a port to it's FreeBSD roots.

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Question regarding Metadata Special Device (lemmy.sdf.org)

submitted 6 days ago* (last edited 6 days ago) by SexualPolytope@lemmy.sdf.org to c/zfs@lemmy.world

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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.

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[–] bob_zim@infosec.exchange 2 points 6 days ago (1 children)

@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.

[–] SexualPolytope@lemmy.sdf.org 1 points 6 days ago

Thanks for the reply. It seems I can't exactly do what I want here.