How to Increase OpenBSDs Resilience to Power Outages

17 pointsposted 9 hours ago
by currysausage
(zlhgo.com)

7 Comments

lotrjohn

3 hours ago

Reader beware. Article is from 2022 and stuff has probably changed a lot. OpenBSD is currently in version 7.9, article talks about 6.6.

Also the PC Engines APU2 the author speaks about is EOL and no longer in production.

I do like how the article is clearly dated at the top. I believe all internet articles should be dated - it provides a huge amount of context imo.

adrian_b

6 minutes ago

I doubt that anything could have changed, because OpenBSD has not implemented any new file system and a few years ago they have even removed the support for "UFS with soft updates", which is a file system that is not affected by power failures, but the OpenBSD developers could not maintain it, because apparently today nobody understands it any more.

Thus there is no doubt that the UFS variant used by OpenBSD remains very sensitive to power failures, so this will remain a persistent problem, until they add a more resilient file system.

The right technical solution would have been to merge a good Linux file system, e.g. XFS, but that is impossible because of license conflicts.

The alternative is to take ZFS from FreeBSD, which might be OK, but I do not know this for sure, because on FreeBSD I use only "UFS with soft updates" which works fine for me and it is still immune to power failures.

ButlerianJihad

5 hours ago

Filesystem fragility is the #1 embarrassment of Unix since time immemorial, and it is shameful that Linus and all the BSD developers cannot be arsed with a default filesystem that is robust and resilient in this regard.

I was just crowing the other day with my parents about the filesystem resilience of the simple Amiga Workbench system. I reminded Dad how you can't just pull the plug on Windows since 3.0. You can't pull the plug on DOS if you're in an app, for that matter. But Amiga, you could just hit the power button whenever you pleased, and the filesystem was none the worse for wear, because it was designed well.

Back in the heyday of Raspberry Pi 3, I was tinkering with a kit, but I moped into a Linux User Group meeting, complaining how often I'd ruined an sdcard filesystem after being forced by circumstance to pull the plug. And a nerd, an AWS Engineer by profession, ignored or misread the situation of the humble SBC, and he told me 'just install ZFS' and also 'stop pulling the plug'.

He did not understand the Raspberry Pi, and I let him know exactly how I felt about his idiotic, misplaced advice. Yes, sure, ZFS for the big systems with gobs of memory and UPS backups. Personally I kinda liked btrfs.

Also the author of today's article cannot spell "gigabytes" and for a storage specialist, that's a real bad look, kids. Learn how to abbreviate, and you communicate better. Spell your units wrong, and you appear uneducated and inexperienced.

But any filesystem in 2026 that simply can't survive a power-cut does not deserve to be in an OS that is High Availability and Redundant and promising >4 nines of uptime. I mean seriously. If this guy's hacks involve mounting rofs everywhere, then ufs (or whatever OpenBSD still uses) has failed again, in 2026, after 56 years' worth of trying to get it right.

adrian_b

15 minutes ago

File system fragility was indeed still an embarassment of many UNIX-derived file systems, up to twenty years ago and perhaps until more recently, but this is no longer true today.

Even in the early 2000's, there was one UNIX file system, the FreeBSD UFS with "soft updates", which was completely immune to computer crashes caused by power failures or by anything else, at a time when the journaled file systems of Linux, and also NTFS of Microsoft, were still buggy enough that power failures could result in bricked computers, despite their claims that journaling should protect against this.

But since then, most bugs have been fixed and now at least for XFS I know with certainty that it can pass through numerous power failures without any problems and with no filesystem corruption.

segmondy

4 hours ago

Actually it's a shame that motherboards don't provide a battery that will allow the system to save file, even if the battery life is just 30 seconds.

bananamogul

2 hours ago

What exactly about the Amiga FFS made it more fault tolerant?

I’m not sure comparing the file system on a single user workstation where disk is probably quiescent most of the time to the file system used on a busy server is really apples to apples. The Wikipedia article on the Amiga FFS makes it sound like it was an early journaled file system, but not technically superior to anything developed since. It plays back the journal if not shut down cleanly. All modern filesystems do that.

OpenBSD uses FFS btw (not the same FFS as the Amiga).

ButlerianJihad

an hour ago

I ... do not know. I do not know how I came to believe these things. It seems they are false beliefs. The Amiga filesystems were not particularly resilient. I suppose I just finished lying to my parents again. I really should fact-check every damn thing I remember, before talking out my ass about them. I surely live in a fantasy dream world.

Having just read through Wikipedia, though: OpenBSD uses UFS, which layer is referred to as ffs in the userspace. It's potato, potato. The soft-updates should have readily mitigated corruption issues, though they didn't entirely go away. LFS is another component to UFS/ffs, as a formally log-structured filesystem.