UFS Crash and directories now missing

[Alejandro Imass]

On Sat, Apr 28, 2012 at 3:22 AM, Wojciech Puchar
<wojtek at wojtek.tensor.gdynia.pl> wrote:
>> I somewhat agree, but it wasn't a person. I am the only administrator,
>> the only one with root access. The jails were effectively moved to the
>> /usr/local/etc/apache22 of the single that survived at the top level.
>> I'm thinking something between mount, EzJail, the journal and the way
>> MySQL created a great deal of head contention, so something must have
>> gotten corrupted at the directory level like you state, but the
>> strange part is no _data_ corruption as such, because I was able to
>> physically archive the jails, move them to the correct directory and
>
>
> no matter what you do FreeBSD DOES NOT ramdomly move directories. if you are
> sure you didn't move it yourself then it must be machine hardware problem
> but still unlikely.

After a little more research, ___it it NOT unlikely at all___ that
under high distress and a hard boot, UFS could have somehow corrupted
the directory structure, whilst maintaining the data intact. From what
I've learned so far, UFS is actually divided into 2 layers: one that
controls the directory structure and metadata and a lower layer
containing the data, so the directories being screwed up and the data
intact it is actually quite possible.

What I'm trying to do is figure out is how it happened, and try
prevent it from happening again, so instead of dismissing it as
impossibility, I think we all should spend a little time figuring out
how these things can happen and determine how it can be prevented or
reduced.

"Should you find your neighbor's beard catch fire, it's wise to soak one's own"

-- 
Alejandro