Is there any chance of proving a filesystem is correct?
Is this one simple enough that it won’t have bugs??
Given the issues with well-known filesystems like ZFS and BetterFS, why shouldn’t I expect data-losing bugs in this one?
GEFS on OpenBSD: A Early Preview
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Re: GEFS on OpenBSD: A Early Preview
#12Is there any chance of proving a filesystem is correct? Is this one simple enough that it won’t have bugs?? Given the issues with well-known filesystems like ZFS and BetterFS, why shouldn’t I expect data-losing bugs in this one?
I think the premise is basically yes, you should assume there will be data-losing bugs, but:
1. The filesystem should be reasonably good at detecting an error/corruption state and informing you, and
2. You should have backups of said data stored elsewhere, and backups should be tested (e.g. to verify that data can be read back)
Re: GEFS on OpenBSD: A Early Preview
#13Is there any chance of proving a filesystem is correct? Is this one simple enough that it won’t have bugs?? Given the issues with well-known filesystems like ZFS and BetterFS, why shouldn’t I expect data-losing bugs in this one?
What well known data-losing bugs are there in zfs? It can be slow, and resource hungry, but afaik it's about as safe as they come (and I've been using it in prod since solaris 10)
Re: GEFS on OpenBSD: A Early Preview
#14From https://orib.dev/gefs.pdf - > While snapshot consistency is useful to keep data consistent, disks often fail over time. In order to detect corruption, block pointers contain a hash of the data that they point at. If corrupted data is returned by the underlying storage medium, this is detected via block hashes. And if a programmer error causes the file system to write garbage to disk, this can often be caught ear…
I don't think it will compete with ZFS or BTRFS (e.g. I don't think ppl will use GEFS over ZFS or BTRFS for a storage server), but it's a modern, much needed FFS replacement.
Re: GEFS on OpenBSD: A Early Preview
#15Is there any chance of proving a filesystem is correct? Is this one simple enough that it won’t have bugs?? Given the issues with well-known filesystems like ZFS and BetterFS, why shouldn’t I expect data-losing bugs in this one?
What well known data-losing bugs are there in zfs? It can be slow, and resource hungry, but afaik it's about as safe as they come (and I've been using it in prod since solaris 10)
There was a long-running data corruption issue with non-raw sends that was finally found and patched in 2025: https://github.com/openzfs/openzfs-docs/issues/494. But I agree, it's about as safe as they come. I trust it far more than any other file system, in large part due to all its built-in redundancy and the way it makes backups trivial (encrypted sends <3)...
Re: GEFS on OpenBSD: A Early Preview
#16Is there any chance of proving a filesystem is correct? Is this one simple enough that it won’t have bugs?? Given the issues with well-known filesystems like ZFS and BetterFS, why shouldn’t I expect data-losing bugs in this one?
What well known data-losing bugs are there in zfs? It can be slow, and resource hungry, but afaik it's about as safe as they come (and I've been using it in prod since solaris 10)
I never dug into the failure, but I once had a ZFS get to a state where it would crash the kernel on mount, I was able to mount it with checks turned off an recover what was important, but it was a spooky experience. I live on the bleeding edge of file systems for my desktop, I was on reiser4 back when that was fresh, I daily drive bcachefs (it's been great!) Mostly I've been lucky, I don't usually keep an openbsd system around, but I love FreeBSD and I'll give OpenBSD a try with GEFS for sure!
Re: GEFS on OpenBSD: A Early Preview
#17I have been running GEFS for a number of days and it hasnt crashed
248 ├gefs [ctl.1]
249 ├gefs [mutate.2]
250 ├gefs [sweep.3]
251 ├gefs [tasks.-1]
252 ├gefs [readio.4]
253 ├gefs [syncio.5]
254 ├gefs [srvio.-1]
255 ├gefs [stdio.-1]
up 13 days, 15:34:25
send it to production!!
Re: GEFS on OpenBSD: A Early Preview
#18This is great timing considering I'm currently dealing with FFS corruption after my OpenBSD server lost power during a storm.
Are you sure it's not just a dodgy SSD that simply failed to persist data when losing power mid-write? I've had my share of sudden power cuts upon OpenBSD during the past 20+ years, and FFS has so far never gone corrupt on me.
Re: GEFS on OpenBSD: A Early Preview
#19What a wonderful surprise! The nearest thing seem to be modern (v5) XFS + dm-integrity, I'll have to see a comparison once it's stable enough.
A thing ZFS suffers from is fragmentation (no way to defragment in-place nor preallocate so stuff like bittorrent doesn't play well with it), which it justifies with its CoW design, wonder if/how it mitigates the problem.
Re: GEFS on OpenBSD: A Early Preview
#20This is great timing considering I'm currently dealing with FFS corruption after my OpenBSD server lost power during a storm.
Are you sure it's not just a dodgy SSD that simply failed to persist data when losing power mid-write? I've had my share of sudden power cuts upon OpenBSD during the past 20+ years, and FFS has so far never gone corrupt on me.
I do not believe so?
Drive is a 2TB Intel 670p NVMe SSD (INTEL SSDPEKNU020TZ) with 9078 power on hours and 42TBW - so pretty spry, but not at the start of the bathtub curve either.
It was mounted as fast storage for a Bitcoin node.
Perhaps the only 'unique' thing is it is using a NVMe to PCIe adapter card (Synology M2D20) due to this being my "legacy" server that's still rocking a Broadwell chip.