Hardware RAID, software RAID, 3ware 9550SX, level 1 vs. level 5

[David Gaudine <davidg@alcor.concordia.ca>]

I have to set up a system that is totally reliable w.r.t. data 
integrity.  That is, if a disk (or anything else) fails, it's OK if the 
system is down for a few hours, but when it comes back up it has to be 
exactly as it was, i.e. I can't restore from the previous day's backup.  
The obvious solution is to use RAID level 1.  Questions;

- Is level 1 as reliable as level 5?  My understanding is that level 5 
has better performance than level 1, but comparable reliability (maybe a 
bit less, since disaster occurs if 2 out of 3 disks go bad at the same 
time.)

- I need to use RAID for everything, not just some partitions, so the 
root has to use RAID.  I've found lots of websites that describe doing 
that with software (mdadm), but very little about hardware.  Using 
software is cheap and seems to be simple, but I assume hardware gives 
better performance.  Is the performance difference significant?  If not, 
I guess my further questions don't matter.  But I'd rather spend money 
than give up performance.

- Many/most modern motherboards claim to support RAID.  Are any of them 
useful, or do they all just provide a BIOS that fakes it well enough for 
Windows but not for Linux?

- The 3ware 9550SX looks good, and there's even a Sarge install:
     http://www.3ware.com/KB/article.aspx?id=14860
Has anyone tried the installer?  I can't unless I buy the card (and a 
computer to put it in) first.  I don't know whether it will do the whole 
job of allowing me to properly set up everyting on RAID at installation 
time, although that seems like the point of having it in an ISO instead 
of just having a driver module.

- Any other ideas about a RAID board that's supported by a Sarge install 
or for which there are step-by-step instructions how now to install 
Sarge and then move it to RAID as is frequently done for mdadm?

David