Bcachefs may be headed out of the kernel

The reiserfs code was stable and in maintenance mode. All new development effort was going into reiser4, which absolutely did die off. IIRC a few developers (that were already working on it) tried to continue the development, but it was abandoned due to lack of support and funds.

In terms of maturity, bcachefs is closer to production quality than reiser4 was, but it's still closer to reiser4 than reiserfs in its lifecycle.

we're further along than btrfs in "will it keep my data"

Fair enough, I have no practical experience with bcachefs myself.

Fair :) I've been trying to keep this thing (relatively) quiet and low profile until it's completely done, but it's gotten hyped.

Data integrity, core IO paths, all the failure modes, all the crazy repair corner cases - these are the hard parts if you really want to get a filesystem right. These are what we've been taking our time on.

I can't claim 100% success rate w.r.t. data loss, but it's been phenomenally good, with some crazy stories of filesystems we've gotten back that you'd never expect - and then it just becomes the norm.

I love the crazy bug reports that really push the boundaries of our capabilities.

That's an attitude that reiserfs and btrfs never had, and when I am confident that it is 100% rock solid and bulletproof I'll be lifting the experimental label.

> we're further along than btrfs in "will it keep my data"

Honestly Kent, this continuing baseless fearmongering from you about btrfs is absolutely disgusting.

It costs you. I was initially very interested in bcachefs, but I will never spend my time testing it or contributing to it as long as you continue behave this way. I'm certain there are many many others who would nominally be very interested, but feel the same way I do.

Your filesystem charitably gets 0.001% the real world testing btrfs does. To claim it is more reliable than btrfs is ignorant and naive.

Maybe it actually is more reliable in the real world (press X to doubt...), but you can't possibly know yet, and you won't know for a long time.

I'm happy to support that bcache may have a stable on disk format, but the lashing out at the alternatives is another example of behaviour I'd prefer to see dropped.

If your product is so great its it's own advert. If it has problems spend the limited person power fixing it not attacking the opposition, this is what ciq have done, do better.

We have documented, in this very thread, issues with multi device setups that btrfs has that bcachefs does not - and btrfs developers ignoring these issues.

This isn't baseless fearmongering, this is "did you think through the failure modes when you were designing the basics".

This stuff comes up over, and over, and over.

Engineering things right matters, and part of that absolutely is comparing and documenting approaches and solutions to see what went right and what went wrong.

This isn't a popularity contest, and this isn't high school where we form into cliques and start slinging insults.

Come up with facts, documentation, analysis. That's what we do. I'm tired of these threads degenerating into flamewars.

(That's impressive, but the real world user pool is much smaller isn't. It still sounds like a proud brag more than it does proven by workload.)

I am not a filesystems guy, but I was disappointed when I realized that btrfs did not have a good design for ENOSPC handling.

So I'm curious, does bcachefs design for a benign failure mode when out of space?

We have enough user reports of multi device testing that they put both bcachefs and btrfs through, where bcachefs consistently survives where btrfs does not. We have much better repair and recovery, with real defense in depth.

Now: I am not saying that bcachefs is yet trouble free enough for widespread deployment, we're still seeing cases where repair needs fairly minor work, but the filesystem may be offline while we get that fixed.

OTOH we also recover, regularly, from absolutely crazy scenarios involving hardware failure: flaky controllers, lightning strikes, I've seen cases where it looked like a head crashed - took out a whole bunch of btree nodes in similar LBA ranges.

IOW: the fundamentals are very solid, but keep checking back if you're wondering when it'll be ready for widespread deployment.

Milestones to watch for: - 3 months with zero data loss or downtime events: I think we may get this soon, knock on wood - stable backports starting: 6.17, knock on wood (or maybe we'll be out of the kernel and coming up with our own plan, who knows) - weird application specific bugs squashed: these have been on the back burner, but there's some weird stuff to get to still (e.g. weird unlink behavior that affects docker and go builds, and the Rust people just reported something odd when building certain packages with mold).

And yes, we've always handled -ENOSPC gracefully.

From my experience as a [x,z]fs snob, "further along than butterfs" is damning with faint praise.

I have used BTRFS for 6 years on 5 drives without a single journaled corruption.

> I have no practical experience with bcachefs myself.

Who does?

When the MySQL and Postgres projects recommend it, I’ll have a look.

That's still a ways off, but it is worth noting that bcachefs handles database workloads in cow mode with no issue.

I haven't lost data on btrfs but I have broken half the partitions I made with it. The comparison doesn't feel baseless to me.

> 0.001% the real world testing

Statistics can be quite powerful. If you have a million installs, and your billion-install competitor has 100 problems per million installs, you can make some pretty strong statements about how you rate against that competitor. Just for easy example numbers.

btrfs is used by numerous NAS providers at this point.

Do you know any that use it in multi device mode?