[TriLUG] Problem with LVM

[T. Bryan]

On Saturday 03 June 2006 09:14 pm, Brian McCullough wrote:

> > 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.

Okay.  Thanks.

> > > 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.  

Yes and no.  I am also trying to use LVM on top of a RAID 1 device.  Of 
course, since this is the first time I've created a software RAID under 
Linux, and it's also the first time I've used LVM....yeah, a bit of 
confusion.  :)

> 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!

I think that he's fine.  I don't think that I was.  My notes say that the 
first time I tried this, I did the following. 

Created /dev/hde1 and /dev/hdg1 as Linux partitions

Formatted both partitions as ext3

Created the RAID device /dev/md0 using /dev/hde1 and /dev/hdg1 

Created a physical volume on /dev/md0

Created a volume group on /dev/md0

Then the rest of the stuff that matched what Rick had done last time: creating 
volume groups, formatting the logical devices, mounting the logical devices.


So....when I try this again, I'll set the partition type to LVM, and I'll skip 
the part where I formatted the partition.  Perhaps that's how I got myself 
into trouble.  :)

---Tom