[TriLUG] new SATA drive 101

[Brian McCullough]

On Mon, Oct 23, 2006 at 01:30:00PM -0400, Christopher L Merrill wrote:
> 
> Thanks - those commands confirm both my assumptions and yours.
> 
> Since I've already added an additional IDE drive (/dev/hdc) once without
> even realizing that LVM was there, I assume that I don't need to use
> it to add this new SATA drive?  I can just follow my usual steps of
> fdisk, parted, edit /etc/fstab, etc?
> 
> (this drive is just going to be a place to archive large files - mapped
> into the filesystem at /backup or something)


However, this is a GREAT chance for you to learn some of the benefits of
LVM.  One of the first ones that you will learn is flexibility.  Let's
say for argument's sake, that this is a 100 GB drive. ( more or less,
since drive size numbers and actual sizes are different )


If you do it your way, you need to decide beforehand how many partitions
you want to use, how big each one is, and what filesystem type each one
should be, and those decisions are then cast in concrete.


Using LVM(2), you create one partition ( usually ) that covers the whole
disk, and call it type "LVM Partition". ( I should be looking at fdisk
to get the names absolutely correct, but you get the idea. ) That will
be type "8e".

You then run the "pvcreate" command.

Next, where things get interesting, you _could_ run "vgextend" and add
the new space to your existing Volume Group, but I would recommend that
you run "vgcreate" and create a completely new Volume Group, called
"MerrillVG" or "MyVG" or anything else you like, using the new drive as
the "seed space".

Finally, you create one or more Logical Volumes from that Volume Group.
Suppose that you decide that you have 5GB of pictures that you want to
save, but that you could add more.  OK, run "lvcreate" and create a 10GB
space, run "mke2fs -j" and mount that new space under /backup/pics or
anywhere else you like.  Then, as time goes on, you discover that you
have filled /backup/pics to 9.75GB.  The exciting part is that you can
simply go back and extend that space to 15GB and continue using it.

If you fill up your 100GB disk, you can add another drive to the system
and keep on extending your Logical Volumes, as if they were infinitely
variable-sized partitions on some vast virtual drive.


Have fun!


Brian