[BozemanLUG] Questions on RAID & LVM

[R. Potter]

I really don't have much experience with RAID and LVM and I am faced 
with playing with both technologies.

I am setting out to build a total of 3 servers.  These servers will be 
built using Ubuntu and software RAID.  I am not looking to have the 
hardware/software debate, but I am looking for some guidance and 
insight.  I am  hoping some of you can offer that.

Server one: built using HP ProLiant with QuadCore Xeon, 4 GIG's of RAM 
and two 1 TB Hard drives.  Server can take four 1TB HD's but nothing 
over 1TB per drive.  Corporate suggested I build this using an LVM so 
that if need be I can expand the capabilities.  However, I am only 
planning on running RAID 1 with this system.  This storage server will 
hold data for two departments who currently are storing just shy of 100 
GIG's.

Server two & three: Both of these remaining two servers will be 
dedicated to one department each and both departments are currently 
storing slightly more than 500 GIG's.  That means I need to either find 
servers that have no 1TB per drive limit, or I need to purchase four 1 
TB HD's and plan to run RAID 1+0.

Question 1: If the first server is only storying 100 Gig's after roughly 
2 or 2 1/2 years and current configuration without LVM would be a 1 TB 
RAID 1 system, Is there any benefit to setting up an LVM?

Question 2: Like question one, is there any good reason to setup an LVM 
on the other two servers if server is maxed out on qty of HD's and total 
HD capacity (4 x 1TB)?

Question 3: I have been reading the Ubuntu instructions for setting up 
the software RAID and the instructions pretty much walk you through the 
process.  But then after the RAID instructions are complete they offer 
the LVM instructions but the LVM instructions make it sound like you 
don't setup RAID first.  Is that a correct understanding, that LVM come 
before RAID?

Question 4: Based on question 3, if I am understanding the LVM 
instructions, I would setup the two or four HD's as individual drives, 
then setup LVM followed by RAID on top of the LVM - or RIAD'ing the 
LVM.  Would that be correct?

Question 5: The instructions from Ubuntu indicated that there were three 
types of LVM, Volume Group, Logical Volume, and Physical Volume.  If I 
should setup an LVM based system, which of the three types of LVM would 
you all recommend?

I know there are several questions and most of them probably will 
require more than one word answers, but if any of you have the time to 
share your experience/view points I would appreciate it.

Thank you,

Rob Potter