this post was submitted on 24 Aug 2024
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There's been some Friday night kernel drama on the Linux kernel mailing list... Linus Torvalds has expressed regrets for merging the Bcachefs file-system and an ensuing back-and-forth between the file-system maintainer.

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[–] solrize@lemmy.world 93 points 2 months ago (62 children)

Can someone say why bcachefs is interesting? Btrfs I can sort of understand. I haven't much kept track of most others.

[–] pimeys@lemmy.nauk.io 51 points 2 months ago* (last edited 2 months ago) (15 children)

For me the reason was that I wanted encryption, raid1 and compression with a mainlined filesystem to my workstation. Btrfs doesn't have encryption, so you need to do it with luks to an mdadm raid, and build btrfs on top of that. Luks on mdadm raid is known to be slow, and in general not a great idea.

ZFS has raid levels, encryption and compression, but doesn't have fsck. So you better have an UPS for your workstation for electric outages. If you do not unmount a ZFS volume cleanly, there's a risk of data loss. ZFS also has a weird license, so you will never get it with mainline Linux kernel. And if you install the module separately, you're not able to update to the latest kernel before ZFS supports it.

Bcachefs has all of this. And it's supposed to be faster than ZFS and btrfs. In a few years it can really be the golden Linux filesystem recommended for everybody. I sure hope Kent gets some more help and stops picking fights with Linus before that.

[–] possiblylinux127@lemmy.zip 1 points 2 months ago* (last edited 2 months ago) (3 children)

ZFS doesn't have Linux fsck has it is its own thing. It instead has ZFS scrubbing which fixes corruption. Just make sure you have at least raid 1 as without a duplicate copy ZFS will have no way of fixing corruption which will cause it to scream at you.

If you just need to get data off you can disable error checking. Just use it at your own risk.

[–] pimeys@lemmy.nauk.io 1 points 2 months ago (1 children)

But scrub is not fsck. It just goes through the checksums and corrects if needed. That's why you need ECC ram so the checksums are always correct. If you get any other issues with the fs, like a power off when syncing a raidz2, there is a chance of an error that scrub cannot fix. Fsck does many other things to fix a filesystem...

So basically a typical zfs installation is with UPS, and I would avoid using it on my laptop just because it kind of needs ECC ram and you should always unmount it cleanly.

This is the spot where bcachefs comes into place. It will implement whatever we love about zfs, but also be kind of feasible for mobile devices. And its fsck is pretty good already, it even gets online checks in 6.11.

Don't get me wrong, my NAS has and will have zfs because it just works and I don't usually need to touch it. The NAS sits next to UPS...

[–] possiblylinux127@lemmy.zip 1 points 2 months ago (1 children)

I have never had an issue with ZFS as long as there is a redundant copy. A bad ram might cause an issue but that's never happened to me. I did have a bad motherboard that corrupted data on write. ZFS threw its hands up but there wasn't any unfixable corruption

[–] pimeys@lemmy.nauk.io 1 points 2 months ago

Me neither, but the risk is there and well documented.

The point was, ZFS is not great as your normal laptop/workstation filesystem. It kind of requires a certain setup, can be slow in certain kinds of workflows, expects disks of same size and is never available immediately for the latest kernel version. Nowadays you actually can add more disks to a pool, but for a very long time you needed to build a new one. Adding a larger disk to a pool will still not resize it, untill all the disks are replaced.

It shines with steady and stable raid arrays, which are designed to a certain size and never touched after they are built. I would never use it in my workstation, and this is the point where bcachefs gets interesting.

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