RAID questions

["Jean-Christian Imbeault" <jean_christian@example.com>]

Ok, I've been doing some reading on RAID. I think I have the basics down but 
a few questions came up. Could some one clarify the following for me?

1- What's the advantage of RAID level 1 versus level 5? They both seem to 
offer redundancy.

2- Is it still the case that you have the whole system under RAID. This 
because having system files and a bootable RAID system is contra-indicated. 
(Or at least causes so much sysadmin pain it's not worth it)

3- How do you know when a disk has failed?

4- How easy is it to replace a failed disk and have the system back up?

I'm thinking of setting up a mail server at out office and I was thinking 
that since it is somewhat of a mission critical system installing RAID would 
be a good idea. To protect against disk failure I tought RAID would be a 
good idea. But maybe there are better ways than RAID?

Jc
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