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[rant] everytime i give it a chance, btrfs lets me down (lemmy.eco.br)
submitted 1 week ago by bunitor@lemmy.eco.br to c/linux@lemmy.ml
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i've instaled opensuse tumbleweed a bunch of times in the last few years, but i always used ext4 instead of btrfs because of previous bad experiences with it nearly a decade ago. every time, with no exceptions, the partition would crap itself into an irrecoverable state

this time around i figured that, since so many years had passed since i last tried btrfs, the filesystem would be in a more reliable state, so i decided to try it again on a new opensuse installation. already, right after installation, os-prober failed to setup opensuse's entry in grub, but maybe that's on me, since my main system is debian (turns out the problem was due to btrfs snapshots)

anyway, after a little more than a week, the partition turned read-only in the middle of a large compilation and then, after i rebooted, the partition died and was irrecoverable. could be due to some bad block or read failure from the hdd (it is supposedly brand new, but i guess it could be busted), but shit like this never happens to me on extfs, even if the hdd is literally dying. also, i have an ext4 and an ufs partition in the same hdd without any issues.

even if we suppose this is the hardware's fault and not btrfs's, should a file system be a little bit more resilient than that? at this rate, i feel like a cosmic ray could set off a btrfs corruption. i hear people claim all the time how mature btrfs is and that it no longer makes sense to create new ext4 partitions, but either i'm extremely unlucky with btrfs or the system is in fucking perpetual beta state and it will never change because it is just good enough for companies who can just, in the case of a partition failure, can just quickly switch the old hdd for a new one and copy the nightly backup over to it

in any case, i am never going to touch btrfs ever again and i'm always going to advise people to choose ext4 instead of btrfs

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[–] Markaos@discuss.tchncs.de 8 points 5 days ago

My two cents: the only time I had an issue with Btrfs, it refused to mount without using a FS repair tool (and was fine afterwards, and I knew which files needed to be checked for possible corruption). When I had an issue with ext4, I didn't know about it until I tried to access an old file and it was 0 bytes - a completely silent corruption I found out probably months after it actually happened.

Both filesystems failed, but one at least notified me about it, while the second just "pretended" everything was fine while it ate my data.

[–] sadTruth@lemmy.hogru.ch 12 points 5 days ago

I am running BTRFS on multiple PCs and Laptops since about 8-10 years ago, and i had 2 incidents:

  1. Cheap SSD: BTRFS reported errors, half a year later the SSD failed and never worked again.
  2. Unstable RAM: BTRFS reported errors, i did a memtest and found RAM was unstable.

I am using BTRFS RAID0 since about 6 years. Even there, i had 0 issues. In all those years BTRFS snapshoting has saved me countless hours when i accidentially misconfigured a program or did a accidential rm -r ~/xyz.

For me the real risk in BTRFS comes from snapper, which takes snapshots even when the disk is almost full. This has resulted in multiple systems not booting because there was no space left. That's why i prefer Timeshift for anything but my main PC.

[–] BCsven@lemmy.ca 14 points 6 days ago (2 children)

My system has been btrfs since 2017. No issues. Maybe you have random powerloss?

[–] dwt@feddit.org 11 points 6 days ago (2 children)

You know, protecting against Powerloss was the major feature of filesystems in a time gone by…

[–] Atemu@lemmy.ml 5 points 6 days ago* (last edited 6 days ago) (1 children)

It only works if the hardware doesn't lie about write barriers. If it says it's written some sectors, btrfs assumes that reading any of those sectors will return the written data rather than the data that was there before. What's important here isn't that the data will forever stay in-tact but ordering. Once a metadata generation has been written to disk, btrfs waits on the write barrier and only updates the superblock (the final metadata "root") afterwards.

If the system loses power while the metadata generation is being written, all is well because the superblock still points at the old generation as the write barrier hasn't passed yet. On the next boot, btrfs will simply continue with the previous generation referenced in the superblock which is fully committed.
If the hardware lied about the write barrier before the superblock update though (i.e. for performance reasons) and has only written e.g. half of the sectors containing the metadata generation but did write the superblock, that would be an inconsistent state which btrfs cannot trivially recover from.

If that promise is broken, there's nothing btrfs (or ZFS for that matter) can do. Software cannot reliably protect against this failure mode.
You could mitigate it by waiting some amount of time which would reduce (but not eliminate) the risk of the data before the barrier not being written yet but that would also make every commit take that much longer which would kill performance.

It can reliably protect against power loss (bugs not withstanding) but only if the hardware doesn't lie about some basic guarantees.

[–] FuckBigTech347@lemmygrad.ml 2 points 4 days ago

I had a drive where data would get silently corrupted after some time no matter what filesystem was on it. Machine's RAM tested fine. Turned out the write cache on the drive was bad! I was able to "fix" it by disabling the cache via hdparm until I was able to replace that drive.

[–] BCsven@lemmy.ca 4 points 6 days ago

Yep, this entry explains about btrfs zfs and powerloss reovery, but that buggy hardware could mess with that system. https://unix.stackexchange.com/questions/340947/does-btrfs-guarantee-data-consistency-on-power-outages#520063

[–] ReversalHatchery@beehaw.org 5 points 5 days ago (1 children)

Maybe you have random powerloss?

who doesn't? even if rarely, but it just happens

[–] BCsven@lemmy.ca 2 points 5 days ago

I lost data on Windows in 2010. Since them I have had a decent UPS. Cheap insurance

[–] zarkanian@sh.itjust.works 12 points 6 days ago (6 children)

Have you tested your RAM?

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[–] ikidd@lemmy.world 1 points 4 days ago

I have had small issues with btrfs over the years, but nothing like the dataloss issues people reported a few years back that the devs supposedly fixed. Its scrubbing mechanism doesn't work great, and the failure modes on RAID are fucking goofy. I wouldn't trust it for raid at all, and they've never really fixed the bugs that have been exposed over the years.

Frankly, it does everything worse than ZFS except for be in the kernel. DKMS isn't that hard and I've never had a ZFS build hook fail. The only thing I use btrfs for is cattle computers that I can nuke and pave at will, and most of those could use ext4 just fine, but that's what Fedora uses by default and I can't be arsed to partition manually.

[–] Endymion_Mallorn@kbin.melroy.org 10 points 6 days ago

This is just telling me that my loyalty to FAT(32) is valid.

[–] yozul@beehaw.org 5 points 6 days ago (2 children)

I mean, unless you really like one of the weird bells and whistles btrfs supports ext4 is just faster and more reliable. If you don't have weird power user needs then anything else is a downgrade. Even ZFS really only makes a significant difference if you're moving around gigabytes of data on a daily basis. If you're on a BSD anyway feel free to go for it, but for most people there is no real benefit. Every other fancy new file system is just worse for typical desktop use cases. People desperately want to replace ext4 because it's old, but there's just really nothing to gain from it. Sometimes simple and reliable is good.

[–] ProgrammingSocks@pawb.social 2 points 4 days ago* (last edited 4 days ago) (1 children)

Copy on write, compression, and snapshots are really good whistles, though.

[–] yozul@beehaw.org 1 points 3 days ago (1 children)

Copy on write is pretty overrated for most use cases. It'd be nice to have, but I don't find it's worth the bother. Disk compression and snapshots have had solutions for longer than btrfs has existed, so I don't understand why I'd want to cram them into an otherwise worse file system and call it an improvement. I will admit that copy on write and snapshots do at least have a little synergy together, but storage has gotten to be one of the cheapest parts of a computer. I'd rather just have a real backup.

[–] ProgrammingSocks@pawb.social 1 points 3 days ago (1 children)

Myself and many others have found lots of use in these features. If it's not important to you that's fine, but there ARE reasons many of us default to btrfs now.

[–] yozul@beehaw.org 1 points 3 days ago

Sure, if it's making your life easier or making you happy or whatever, then have it. Don't let me yuck your yum. I just think it doesn't provide any real benefit for most people. Am I not allowed to talk about my opinion?

[–] ReversalHatchery@beehaw.org 5 points 5 days ago* (last edited 5 days ago) (2 children)

being able to revert a failed upgrade by restoring a snapshot is not a power user need but a very basic feature for everyday users who do not want to debug every little problem that can go wrong, but just want to use their computer.

ext4 does not allow that.

[–] yozul@beehaw.org 2 points 4 days ago (1 children)

You know file systems are not the only way to do that, right? Heck, Timeshift is explicitly designed to do that easily and automatically without ever even having to look at a command line. Backup before upgrade is a weird thing to cram into a file system.

[–] ReversalHatchery@beehaw.org 1 points 4 days ago

Timeshift is explicitly designed to do that easily and automatically

by consuming much more space. but you're right, I did not think about it

Backup before upgrade is a weird thing to cram into a file system.

I agree, but these are not really backups, but snapshots, which are stored more efficiently, without duplicating data. of course it does not replace an off site backup, but I think it has its use cases.

[–] Unmapped@lemmy.ml 2 points 5 days ago (1 children)

By using NixOS I can do this on ext4. Just reboot back to the previous image before the update. Not saying everyday users should be running nixos but there are other Immutable distros that can do the same.

[–] ReversalHatchery@beehaw.org 2 points 4 days ago (1 children)

will that also restore your data? what happens when a program updates its database structure with the update, and the old version you restore won't understand it anymore?

[–] Unmapped@lemmy.ml 2 points 4 days ago (1 children)

That is a good point. I've only had to rollback twice and nether time had any issues. But from my understanding of how it works, you are correct, the data wouldn't rollback.

[–] ReversalHatchery@beehaw.org 2 points 4 days ago

I've learned this lesson with my Android phone a few years ago. There it was actually about sqlite databases of a system app (contacts I think?), but this can happen with other formats too. Worst is if it doesn't just error out, but tries to work with "garbage", because it'll possibly take much more time to debug it, or even realize that your data is corrupt.

[–] WalnutLum@lemmy.ml 9 points 6 days ago

I've had btrfs go into an error state because of a bad write before, but it was pretty easy to recover from

[–] blackstrat@lemmy.fwgx.uk 6 points 6 days ago (1 children)

You're right to give up on btrfs. It's been so long in development and it just isn't ready. Ext4 or ZFS are mature and excellent file systems. There's no need for btrfs these days. It always has and always will disappoint.

Everyone singing the praises of it are the sysadmin equivalent of the software engineer yelling 'it works on my machine' when a user finds an issue.

[–] LiamMayfair@lemmy.sdf.org 5 points 5 days ago (1 children)

I can't comment on its server use cases or exotic workstation setups with RAID, NAS, etc. but I've been running Fedora on Btrfs for quite a few years now and I've had zero issues with it. Am I deliberately using all of its features like CoW, compression, snapshots...? No, but neither would your average Linux user who just wants something that works, like ext4.

I don't miss ext4, Btrfs worked for me since day 1.

[–] blackstrat@lemmy.fwgx.uk 3 points 5 days ago (2 children)

So, what you're saying is, "it works on my machine"

[–] cool_pebble@aussie.zone 9 points 5 days ago (1 children)

Aren't we all? Aren't Ext4 and ZFS considered mature because so many people have said "it works on my machine"?

I agree this person's experience may contrast to your own, but I don't think the fact that something has worked well for some people, and perhaps not for yourself, is a reason to discount it entirely.

[–] blackstrat@lemmy.fwgx.uk 3 points 5 days ago

I've never heard anyone say ZFS broke, corrupted their data or failed in any way at all. With btrfs it's a consistent complaint. And btrfs literally has modes of operation that are known to be broken. I could understand if it was a new file system, but it can almost drink in pubs.

[–] kyoji@lemmy.world 1 points 4 days ago

And everyone else's that uses Fedora?

[–] unknowing8343@discuss.tchncs.de 3 points 5 days ago

Been using BTRFS since I learned I could squeeze more data on my cheap-ass drive and... It's been 3 years, no problem at all, and I have backups anyway.

[–] data1701d@startrek.website 6 points 6 days ago

Sad to hear. I don’t know if it’s luck or something else.

I’ve been running Debian on btrfs on my laptop for 3 months without issue; I still use ext4 on my desktop, as I just went with defaults when I installed the operating system.

[–] canadaduane@lemmy.ca 1 points 4 days ago

I had some trouble with ZFS and kernel compatibility when upgrading the OS, so I switched to btrfs. It's been fine for 3 years now, including a kernel upgrade.

[–] yum13241@lemm.ee 1 points 5 days ago (1 children)

I literally daily drive btrfs. Just don't use a crappy drive or use raid5/raid6.

[–] FuckBigTech347@lemmygrad.ml 1 points 4 days ago

BTRFS RAID5/6 is fine as long you don't run into a scenario where your machine crashes and there was still unwritten data in the cache. Also write performance sucks and scrubbing takes an eternity.

[–] jaypatelani@lemmy.ml 3 points 6 days ago (4 children)

Get on FreeBSD + ZFS

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