Choosing a fault-tolerant file system for FreeBSD?

Question

FreeBSD

Something terrible happened to me today, and I'm at a loss.
Chronicle of a diving FS:
- all day 01.06 - changes in the application code, writing to the UFS volume as it was created when FreeBSD 8.2 was installed (mount ufs, local, noatime, soft-updates), background_fsck="NO".
- in the evening I set up a tunnel to the main server, I decided to back it up as soon as I get home
- after three hours the server does not answer, there is no one in the office
- in the morning I asked to turn on the server (it was turned off, it worked according to a temporary scheme without UPS through a regular network filter)
- interrogation with by the addiction of the local Gulchatai (cleaning lady) he gave out “a tyrant, I turned off the filter, then turned it on”
- all files that changed on that day (01.06) have zero length

I eventually restored the files (the included backup of changes in the editor is good), but the questions remained:
1. Why exactly these files were killed, especially considering that the server was rebooted 5 times, it was also rebooted before I left, and all the files were in place (not very important).
2. How to make sure that this does not happen? :)
It is clear that there will be UPS, but still ...
At the same time, the performance of the volume itself does not really matter, only the reliability of storage matters (the office is remote, you won’t run into it). Ideally, find a solution that, with the Apache root and mysql database installed on the usb disk, would allow you to turn off the electricity, pull the disk out of usb, with a stupid rollback to the previous working state. Is that possible? But as? And if a volume has already been created there and the data is lying there?
Thanks in advance to the gurus for the answers, I have a temporary collapse of my thinking muscles now ... :(
UPDATE : created three partitions on the usb disk, raised the zpool mirror on two, on the third spare, set copies = 2.
Something will survive ... : )

Answer 1

And what about the idea to build a RAID array?
In some cases, hemorrhoids, but it's worth it!

Answer 2

Yes, it seems that ZFS is already possible on all partitions, including the root one. Why not him?