I've 100% had issues with UFS, it's a simple filesystem and subsceptible to corruption. ZFS meanwhile is a different beast altogether which is designed to ensure data integrity at all costs.
UFS without soft updates is easily susceptible to corruption.
The "soft updates" option must be chosen when the disk is formatted for good reliability.
As I have said, 20 years ago "soft updates" in UFS worked better than journaling in the other contemporaneous file systems.
Nowadays it is likely that this is no longer true. I am still using FreeBSD in servers, but unlike 20 years ago I can afford UPSes so I no longer see often crashes due to power outages, even if I had one incident some time ago with a battery that had not been replaced yet after the UPS had warned that this is necessary, and when a power outage happened, the UPS worked for less than a minute and the power was cut before system shutdown. Even in this case there was no file system corruption on UFS.
Even with this good recent experience, today I would no longer trust UFS like 20 years ago, because it is said the current FreeBSD maintainers no longer understand the convoluted code that implements "soft updates" in UFS, and in any case most of their file system maintenance and development work is directed at ZFS now.
Although, according to the link, not because there's anything wrong with it, but because other changes they want to make to the filesystem code would risk breaking soft updates.
Softdep is a significant impediment to progressing in the vfs layer
so we plan to get it out of the way. It is too clever for us to
continue maintaining as it is.
UFS on FreeBSD is still maintained bz Kirk McKusick, the inventor of soft updates. It's the other BSDs that have trouble as they can't rely on Kirk's expertise.
ZFS had its own data corruption bug some months ago.
TBH, this was a big minus. You really don't expect such things from a filesystem which is in production for years and whos aim is data integrity.
Now, to its defence, it is only used by FreeBSD and some nishe linux distributions, so it does not get much testing.
