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Cake day: March 1st, 2024

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  • L2ARC is not a read cache in the conventional sense, but something closer to swap for disks only. It is only effective if your ARC hit rate is really low from memory constraints, although I’m not sure how things stack up now with persistent L2ARC. ZFS does have special allocation devices, though, where metadata and optionally small blocks of data (which HDDs struggle with) can go, but you can lose data if these devices fail. There’s also the SLOG, where sync writes can go. It’s often useful to use something like optane drives for it.

    Personally, I’d just keep separate drives. A lot of caching methods are afterthoughts (bcache is not really maintained as Kent is now working on bcachefs) or, like ZFS, are really complex are not true readback/writeback caches. In particular, LVM cache can, depending on its configuration, lead to data loss if a cache device is lost, and LVM itself can occur some overhead.

    Flash is cheap. A 2TB NVMe drive is now roughly the cost of 2 AAA games (which is sad, really). OP should just buy a new drive.




  • You wouldn’t use Silverblue on a server, you’d use Fedora CoreOS (FCOS) or CentOS Stream CoreOS (COSS). The ublue project has a FCOS derivative called ucore with options for ZFS OOTB. I use it on my server.

    There’s some examples on how you’d use dockerfiles to build a ZFS module (as well as other things) from Fedora as well.

    In any case, building bootable container images containing stuff like kernel modules is currently how this type of thing is done on atomic Fedora variants.