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Comment by toastal | Hacker News Reader

How long til it would be recommended to move from ZFS to BcacheFS on Linux?

10+ years, considering how Btrfs has played out.

Btrfs was merged in 2009, but didn't gain wide acceptance until quite recently. Among the biggest distros, only Fedora uses it as default, and RHEL has actually dropped support. Even today, you can still find people claiming that they lost data because of it, though whether they are telling the truth I cannot say.

btrfs was merged in Linux in a very different state than bcachefs is now; bcachefs already has about ten years of development behind it, whereas btrfs "only" had two years of development behind it when it was merged. It would almost certainly not be merged today.

I'm not saying you should switch all your critical systems to bcachefs on the day it gets merged as you can never be sure about the absence of bugs (even the relatively simple ext4 had some data-eating bug a few years after introduction), but the path to "recommended filesystem" will be a lot shorter than btrfs.

At this point, I would already feel comfterable running bcachefs on my laptop – the only reason I don't is that I just can't be bothered running a custom kernel for it.

How does bcachefs deal with laptops just dying due to lack of power and then fsck and recover on boot?

Works fine. Been using it on my laptop for ~7 years, users say it's solid w.r.t. power failure too.

Awesome, can't wait for this to become linux's best filesystem.

Apparently, just fine. On paper, do a quick check and clean on mount. There are mount options for full check, degraded and recovery modes. About the paper https://bcachefs.org/bcachefs-principles-of-operation.pdf

I believe openSUSE uses Btrfs.

I haven't lost data on it, but my 8 drive Btrfs RAID6 filesystem locked up read-only on me, which wasn't fun. Switched to ZFS after that.

I have had single-drive btrfs filesystems lock up on me twice; i.e. file manipulation commands like `ls` freeze and "take forever". In both cases, there was a hardware failure of the drive. I believe that the frozen processes went into uninterruptible sleep (so they couldn't be killed).

It is totally understandable that if the underlying driver starts returning errors, btrfs (or any other filesystem) may be unable to provide access to my data; but I was not at all happy about having to reboot the entire machine.

(I must admit, it is possible that the "freezing" was happening in underlying block device driver code and not in btrfs. I don't remember if I ever checked wchan to see which it was. My impression from reading dmesg output was the issue seemed to be with btrfs.)

I did once have a similar experience with ZFS as well. Sigh.

Couple weeks ago had someone complain about system updates and other mildly IO heavy things making his system extremely slow and lock up for minutes at a time, despite having an NVMe SSD. Rebalancing fixed it - which iirc I also had to do regularly about ten years ago when I had the exact same problems with btrfs.

Yeah, OpenSUSE does BTRFS although they also support XFS. I ran tumbleweed for a while and managed to lose a root filesystem twice, although that was a few years ago and appeared to be triggered by running out of space, as the home filesystem on the same box, also BTRFS, survived both times.

RAID5/6 is still quite beta in btrfs. mdadm+btrfs is the way to go here.

Actually any RAID is beta in btrfs, but configurations with one storage device (e.g. firmware of Turris Omnia) do quite well on prod.

No, it's not beta. You can check the status here https://btrfs.readthedocs.io/en/latest/Status.html

Only raid5/6 has known issues.

This was also about 8 years ago. It was originally a RAID1 setup, but I did an in-place converter to RAID6, which is cool. And like I said, I didn't lose any data.

With mdadm, I don't get auto-repair on top of the checksumming.

I got a Btrfs RAID1 corrupted 3 times, so I was loosing faith in Btrfs, then I ran memtest and found out I had a bad memory stick causing real data corruption, not a Btrfs bug.

It is quite understandable that something as critical when it comes to file storage takes a while to be adopted and being tested on less important data first. I'd say this reflects positively on IT.

A nice (and lone) data point regarding btrfs, though: My dentist told me that he was storing patient data using btrfs last year. :)

I can't help but wonder how that conversation happened: Ya so we're going to root canal your molar, ah and by the way patient data is on btrfs which is only slightly worse...

Oh you never lost data with btrfs, but you might give up following the trail of mailing list posts and wikis one fine spring morning when it failed to mount.

ISTR hours-long repair operations and a level of desperation that a lot of people wouldn't have had time for. This is assuming you didn't use its RAID or other features that definitely would eat your data.

(This is experience from 10 years ago when I was looking for the latest and greatest features to support a hosting platform)

Btrfs is significantly more complex and very different case. Bcachefs is designed by single guy with different motivation.

Main problem with Bcachefs is its in unknown state. There was no major testing done on that. When some company (like Oracle or Suse) puts it through automated stress test matrix, it may do exceptionally well or completely fail.

The article discusses having automated testing set up in conjunction with Red Hat's increasing interest in it.

I am not familiar with Red Hat, but other companies have proprietary verification tests. It takes several decades of machine time to complete.

For example Suse participated over 25 years on Ext3,4, ReiserFS/4, XFS, BTRFS.... This know how is not public!

How do you know of Oracle and SUSE but not Red Hat?

Probably meant not familiar with Red Hat’s automated testing?

openSUSE also uses it as the default, as do Synology NAS appliances.

Synology uses mdadm+btrfs for the record.

Still a pretty good endorsement in my mind.

I keep wondering this too, but at the same time, alebit with bugs, I have a ZFS pool mountable under Linux and Windows, so I have decided to not hold my breath at all. Not to mention zrepl, etc.

I recently discovered that btrfs can also be mounted under windows.

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