How to create a terabyte storage array?

['Forum Post]

How difficult is it to extend a Raid 5?  Do you always need 5 drives?  I
currently have a RH8 server with mirrored 80GB drives that I'm now out
of room on.  I want to upgrade it to Ubuntu and I don't want to dump a
ton of money into 4 or 5 drives.  Since the data on it doesn't change
very often (MP3's and family pictures), I have just bought a 250GB
drive and planned on creating one LVM group with it and a 2nd LVM group
with the two 80's.  I was then thinking of having a cron job run every
night that backed up from one LVM group to the other, only copying
files that have changed, been added, or removing ones that no longer
exist.  If I need to extend either LVM group later, it's a non-issue. 
If one of the groups fail, it can be rebuilt from the other.



I know that RAID-5 gives you "instant" redundancy but I don't really
need that with my setup.


-- 
skirkpatrick