[TriLUG] Problem with LVM

[Brian McCullough]

On Sat, Jun 03, 2006 at 07:14:51PM -0400, T. Bryan wrote:
> I put this project on the back shelf for a bit.  Now that I'm ready for it, I 
> invoke the Necromancer to resurrect this thread...

I consider it resurrected ... and so we continue.


> On Monday 01 May 2006 11:47 am, Rick DeNatale wrote:
> 
> > 1) Partition /dev/sdb like /dev/sda
> 
> In this step, what did you do?  Say that I use fdisk to create a whole-disk 
> partition on my drive /dev/hde.  What partition type should I set?  Do I need 
> to create a filesystem on it (with mkfs.ext3, for example), or is all of that 
> somehow taken care of by lvm?

In order:

0 -- Presuming you decide to use the whole disk route:
1 -- Partition type is: "LVM"
2 -- No, you are premature.  LVM creates, in effect, the "disk 
device" itself.  Later on, you will format the "partition" that 
you create.


> > 2) Create the raid array with a missing drive
> > $mdadm --create /dev/md0 --level 1 --raid-devices=2 missing /dev/sdb5
> > 
> > 3) Create a PV on the raid array
> > $pvcreate /dev/md0
> > 
> > 4) create a VG
> > $vgcreate MainVG /dev/md0
> 
> Right...so, what was /dev/sdb5?  Was it an unformatted partition?  Or did you 
> first format it as an ext2 or ext3 filesystem?


Here, Rick is combining two different technologies, that may confuse
you.  The first, which is RAID ( type 1 -- Mirroring ) is what he used 
sdb5 for.  Then he used LVM on top of that RAID device to create, first,
a Physical Volume, and then a Volume Group ( VG ).  Yes it was
unformatted, or if it wasn't he is in trouble!  


Finally, what he did, and you didn't show, was create a Logical Volume,
the equivalent of the old fdisk partition ( what we used to use to make
a space for a file system ), which he sized appropriately and then
formatted as he wished ( ext2 or ext3 or reiser or ... ).  That can then
be mounted and used as you wish.


> Thanks,
> ---Tom


Any time,
Brian

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