Comment by pdimitar
Yeah I know, thanks. But ZFS still mostly requires drives with the same sizes. My main NAS is like that but I can't expand it even though I want to, with drives of different sizes I have lying around, and I am not keen on spending for new HDDs right now. So I thought I'll make a secondary NAS with bcachefs and all the spare drives I have.
As for ZFS, I'll be buying some extra drives later this year and will make use of direct_io so I can use another NVMe spare for faster access.
If you don’t care about redundancy, you could add all of them as top level vdevs and then ZFS will happily use all of the space on them until one fails. Performance should be great until there is a failure. Just have good backups.