[Q] post-crash behaviour

Hello,
I don't know if this the right place to post this, please excuse me if
I'm wrong. I didn't find any clearly appropriate E-mail for this on the
website.

I'm working on a project where we are questionning ourselves about the
reliability of PostgreSQL (our customer wants to compare to Oracle but
it's no matter for my question).

Our main concern is databases files' internal structure corruption.
What is PostgreSQL's behaviour regarding software and hardware failures:
- soft termination of the server (kill -INT),
- hard termination (kill -9, server bug),
- power loss (or disk failure) that occurs in the middle of disk I/O,

I searched the docs and found nothing about this. I also searched
newsgroups with no success.

I would like to know if, in those cases:
- is the server able to restart and operate correctly on correct data
(transaction wise) ?
- if internal file corruption could occur, would the server tell on
startup something like "The database is corrupted, can't start" ?
And this in a deterministic way ?
- or is there a risk that the server could start and run with corrupted
files and data ?

Thanks if anyone can answer this.

--
Best regards,
Fabien COUTANT
STERIA