[KLUG Members] any experience with Debian Sarge & Dell 39160 SCSI controller?

[Adam Tauno Williams]

>> I did a presentation on LVM & MD not too long ago.
>> What do you want to know?  I'm assuming the Debian installer lets you create
>> logical volumes some kind of wizard?
> It appears the Debian installer supports setting up LVM on install. What
> I am trying to figure out and envision is how this works.
> 1) So I setup the 3 drives in RAID 5. This gives me one "disk" to the
> partitioner that the LVM is setup on. Out of that I would setup
> a /boot /var /home and then I usually just leave the rest to /

Sounds reasonable.

> 2) So let's say that /home is getting full and I want to add another
> disk to it. Is it still going to be possible to add the disk to the raid
> array and somehow get that space into the LVM setup? All the docs I see
> have the examples just adding a new disk and mounting it then adding it
> to the LVM space. No one seems to talk about how it works with a RAID
> setup.
> I know I can set it up, what I don't know is if it is going to let me do
> what I want to do which is have a hot-swap disk in the machine and still
> be able to expand the filesystem as needed in the future.

Expanding the filesystem one the drive is added to the array shouldn't be a
problem.   I generally avoid RAID-5, for a myriad of reasons, but also because
it makes this scenario more complicated.  I just run mirroring on drive 
pairs -
so each pair is a RAID pairt (or each four drives is a mirror pair),  
then I add
drives in twos creating a new RAID pair, partition the RAID pair (which as you
said appears to the OS as one drive), and add it to the appropriate volume
group.  This of course requires more drives than RAID 5.

For some interesting reading on RAID 5 see:
http://www.miracleas.com/BAARF/RAID5_versus_RAID10.txt
http://www.miracleas.com/BAARF/1.Millsap2000.01.03-RAID5.pdf

Note: Art Kagel knows more about relational database systems and the various
implementations as well as wringing every last bit of performance out of I/O
subsystems than your average 1,000 system adminsitrations have forgotten -
collectively.

So I can't answer your question as I've never added an additional drive to a
RAID5 array HOT (and HOT is the point).  The last RAID-5 array I had 
was before
the LINUX kernel could rescan a SCSI bus for new devices without crashing. :)