Posted by farlight 3 hours ago
Having that said I'm desperately trying to get REAL hardware to run that benchmark. With some successes ;)
Few months ago I got Hetzner machine from Kent Overstreet and I was able to finish 3 runs before machine died... Results: https://bartosz.fenski.pl/modern-fs-benchmark/real-hw/
Currently I've got even more interesting machine with tons of disks and I'm running new set of benchmarks but it's really in its initial stage.
https://bartosz.fenski.pl/modern-fs-benchmark/sas-hdd/ 2nd run in progress... one run on REAL hardware takes much more time than on GH runner so it's slow.
But this new hardware has also so many disks that the plan is to try also more complex, tiered cache topologies. I'm working on it.
I'm happy to answer any other questions, sources of every piece of this benchmark are freely available and I'm not saying they are 100% correct. I'm open to improvements.
I've been saying it for months, but eventually I'm going to move the automated builds off the 48 core monster and we'll be able to use that for automated perf testing too. The machine we just got has spindles for EC perf testing, but the Hetzner monster has very high end enterprise ssdd.
Also, just got done with the Rust for Linux conference, still not home but here's slides that still need reformatting: https://evilpiepirate.org/~kent/Kangrejos-2026-bcachefs.pdf
1. Dual Ext4 + external 32GB journal X4 pcie SSD (the prior winner of benchmark surveys)
2. Bare F2FS after a trim and SSD vendor software cache flush operation (it should be slower, but knowing how much slower on identical hardware could be interesting.)
3. DRBD across a 48U 100Gbps host rack (single X4 pcie data drive per host, OS on primary)
4. CephFS across a 48U 100Gbps host rack (single X4 pcie data drive per host, OS on primary)
Best regards =3
You can mix devices of different sizes and types on bcachefs. You can have foreground and background devices to balance performance and also different compression settings for foreground and background transactions.
You can set replicas=N to the individual file or directory on bcachefs. For example files you can just re-download or re-build. Likewise you can set a higher number of copies to important files.
Not everyone gets it though, that's for sure.
And, if you want to know if it's mature, I'd trust the user reports over the one liners :)
I think if you're not using baremetal for such tests, it's likely that the results are simply not comparable at all? What if another tenant is also using the disk?
If it's something as simple as a KVM hypervisor that only runs 1 test VM at a time (with no other load from anything else other than the basic systemd daemons, ssh daemon etc running on the hypervisor), the results could be very close to bare metal.
I can see it being very time consuming and annoying to do repeated manual bare metal OS installs and new partitioning/filesystem creation for such a large variety of tests.
The author does also say that performance isn't really the main thing but rather, data integrity:
Well don't do that then. There's lots of other options. Probably the simplest is a single bare metal install on a simple filesystem on one device. run the filesystems under test on other storage dedicated to testing.
You could also boot into a network install and use local storage exclusively for testing.
Also take a look at tests on real hardware. There are not many of them but there are some. I pointed to them in my first answer.
Real hardware is used in: https://bartosz.fenski.pl/modern-fs-benchmark/real-hw/ https://bartosz.fenski.pl/modern-fs-benchmark/sas-hdd/
But unfortunatelly it's much more limited number of actual runs. sas-hdd is still in progress so numbers for it should increase over time.
In this case, given that the author's own disclaimer (above) already disclaims the numeric readings, I'm not sure how it's possible to make any inference on "shapes and ratios" derived from the numeric readings.
I'm saying ZFS on another OS.
I get that real hardware costs (author mentions EUR 70 a month for a suitable server), but without at least a baseline snapshot comparison run between real hardware, both SSD and HDD, and the sparse file-backed loop devices, it's hard to take much away from this.
Sadly the AI apocalypse isn't making stuff like this easy to do as a hobby.
In fact they delivered the erasure coding for parity raid back in march this year.
The thing is that as soon as you seriously give a chance to Bcachefs you see how good it is. I can only tell you that mixing different device tiers and having a per-file/directory replication setting is a god send specially in these times where storage costs more than gold.
I'm pretty sure Bcachefs is amazing and better than Btrfs. I also think Zfs is amazing and better than Btrfs. Even so, I still use Btrfs because I know it is guaranteed to always be present on any Linux without any effort on my part.
> That might be the best thing happened to the project since now development can happen at its own pace without the clicky bait influencers.
A better approach might have been to just paused mainline merging instead of forcing being kicked out?
Eg "Hey Linus, Bcachefs is still in early development and I need to merge changes in a pace that is not compatible with Linux development process. So I'm going to pause for a while now and once it reaches maintenance status I will focus on submitting patches in a healthy pace that you can digest".
I used to think that about ReiserFS, too. It was in the mainline kernel, development was snappy, and it solved some performance problems. I used it all over the place.
Things then subsequently... changed. :-/
100%. My system is rock solid and the last thing I need is rolling the dice after every update on whether my system will boot. https://www.reddit.com/r/archlinux/comments/eywcp7/linux_551...
I'm impressed with bcachefs's accomplishments though, and if they ever reconcile with the kernel I'll surely give it a fair shake.
As for BTRFS I think its also pretty good. Its just that I have the impression its development is guided by the needs of its sponsors and sadly for us META doesn't need RAID5.
A lot of things were tried, people did try to mediate.
The particularly galling thing though was when I finally started looking - post split - comparing bcachefs PRs to other subsystems and especially XFS - I was being more conservative with what I considered a critical bugfix.
There was never a clear statement on what the issue was. What you guys got in public was about as much as I got.
All I can say is - going fast when you're stabilizing and getting bugfixes out the door is what you can and should be doing when you've invested in test coverage, test automation, keeping the codebase clean and asserted, and building up a community that works well together on testing and shaking things out.
I genuinely do not know what they were thinking.
Instead it got kicked out because Kent constantly ignored the kernel's contribution rules and is unlikely it will ever be accepted back into the kernel.
And it went in when it did because Redhat was pushing for it and claiming to be supportive - but that never materialized. They wanted to get something for free without investing, or putting in the absolute bare minimum.
A _lot_ of people were saying publicly and privately "dear god yes we need something better than btrfs" - but no one from the existing kernel community was interested in stepping up.
Community's still growing, though. A lot of people have gotten active in making sure bcachefs actually works well for people end to end, and there's a hell of a lot more to shipping a filesystem than just writing kernel code.
The FS was marked experimental, so there is no urgency in fixing bugs or providing features in a certain cycle. Everyone using it knows what they got themselves into. You can still provide the DKMS module for faster fixes and features for anyone who wants to use BCacheFS more seriously for the time that the upstreaming process takes, but eventually it would have all been on mainline.
Asahi is taking a similar approach where they have their downstream kernel and push things upstream once they are mature.
That means the upstream kernel is not useful for running on that hardware now, but things are moving there eventually.
I do have a lot more pull requests to merge than I did before. I don't know if you want to count "Kent isn't reviewing PRs fast enough" as drama :)