FreeBSD 6.x CVSUP today crashes with zero load ...

[M.Hirsch]

> Ok...
> Does the standard fs, UFS2, do "extra sanity checks", then?
>
Sorry, replying to myself...
No, this does not matter.
If the OS thinks the data is ok, UFS will write OK data...

So, let me rephrase this:
How can I make sure there is no broken hardware in my cluster?
I am not looking for workarounds, like ECC. I want the box to break 
immediately once any single component goes wrong...