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Comment by sidkshatriya | Hacker News Reader

From the blog post:

> Even if your btrfs, after almost 18 years, still eats data in spectacular fashion.

Is this (by now) an urban legend ? Is btrfs any less reliable than, say, xfs/ext4 etc. nowadays ?

SUSE is using btrfs as the default filesystem in all their offerings. I think that SLES is less widespread than RHEL, but I also think those people at SUSE know what they are doing. It's not like we hear of massive data loss from SLES environments all the time.

Even the much-maligned raid5/6 is basically fine†.

If you're concerned about the write hole, use -m DUP/raid1/raid1c2 instead of -m raid5. Plus raid-stripe-tree†† is coming - didn't check the status of it recently.

Many horror stories are because, while btrfs is fine, the operational model and tooling have some footguns which can cause either straight up data loss (due to operator error, but arguably that's really due to bad UX) or possible-but-hard-to-get-out-of situations.

I use btrfs because using zfs has been painful for me, for two reasons:

- btrfs can "shapeshift": I progressively moved _live_ from 2hdd raid1 to 5hdd raid5 data + raid1c2 meta with varying experiments in between. Probably five or six rebalance to change its shape over the years.

- the zfs module situation: when I tried it, the module silently failed to build properly and this resulted in a broken system til I fixed it; this happened twice over six months. Luckily I anticipated this failure mode and only the data array (not the root fs) was zfs, so I could still boot and login into a full system to fix.

Compared to zfs, btrfs is slow to scrub and rebalance though.

† https://unixdigest.com/articles/battle-testing-zfs-btrfs-and...

†† https://lore.kernel.org/linux-btrfs/cover.1698679287.git.dst...

I used btrfs for most of the 2010's. I nearly lost some data once, and was able to recover it. Afterwards, I moved to ZFS and never looked back.

btrfs may be great now, and more power to people who use it and are happy. However, I am so used to the ergonomics of ZFS (and zed, and ZFS integrated encryption) that I don't see a reason to migrate back.

I've lost my laptops SSD (as in: no longer mountable, only got data out of it with some rescue tools) at some point between 2017 and 2020, don't remember when exactly. I've also had a weird experience where a btrfs filesystem formatted on my desktop PC was not mountable on a Raspberry Pi, and vice versa formatted on the Pi was not mountable on the desktop. That didn't instill confidence either.

On the other hand, I've been running a btrfs RAID1 on two HGST datacenter drives for a few years and haven't had issues with that.

  The RAID 5 and RAID 6 modes of Btrfs are fatally flawed, and should not be used for "anything but testing with throw-away data."

From the ArchWiki: https://wiki.archlinux.org/title/Btrfs#Multi-device_file_sys...

No, Linux is made of legends that never die.

BTRFS is fine if you use it on enterprise grade hardware, if you use it on consumer hardware expect to lose data.

Why and how does enterprise vs consumer hardware make a difference wrt btrfs data loss?

Traditionally it was btrfs RAID5/6 that really sucked. I've not played with it.

for features declared stable it's been an urban legend for a long time. I use BTRFS in prod since I think 2016 which was also the last year I lost data to an BTRFS Bug

I wouldn't know I've been running ZFS for well over a decade.

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