CentOS - Oct 2006 - Proper partition/LVM growth after RAID migration

Hi

This topic is perhaps not for this list, but it I'm running on a
CentOS 4.4 and it seems that a lot of people here uses 3Ware and RAID
volumes.

I did a RAID migration on a 3Ware 9590SE-12, so that an exported disk
grew from 700GB to 1400GB. The exported disk is managed by LVM. The
problem now is that I don't really know what to do now to let LVM and
my locigal volume to make use of this new disk size, and probably
future disk size growth.

I initially imagined that I could let the physical partition grow and
then the LVM PV, the LV and the FS (ext3) to grow to fill up the new
exported disk size. Then I realized that this is not how LVM is
designed - you add PVs and let the LV and FS to grow.

But, what if the underlying exported disk from a RAID card is growing
as you add disks to it's RAID volume? Should you create new physical
partitions on the exported disk, and specifically, extended
partitions, since you might in the future add more than 4 partitions?

Secondly, it seems there is a problem after this migration: The
graphical LVM shows that I have an "Unpartitioned space" on the
exported disk, but I can't click on "Initialize entry" button. The
property window on the right says: "Not initializable: Partition
manually".

parted shows only one partition:

[root at acrux ~]# parted /dev/sdb print
Disk geometry for /dev/sdb: 0.000-1430490.000 megabytes
Disk label type: msdos
Minor    Start       End     Type      Filesystem  Flags
1          0.000 715245.000  primary               lvm

fdisk in expert mode (x) shows that partition 2-4 fields are all zeros.

Should I now make a lvm partition in an extended partition in parted,
and then hopefully, the graphical LVM will be able to add the new
physical partition to my logical volume, and then resize my  fs
(ext3)?


Thanks in advance for any input on this,
Christian

> I did a RAID migration on a 3Ware 9590SE-12, so that an exported disk
> grew from 700GB to 1400GB. The exported disk is managed by LVM. The
> problem now is that I don't really know what to do now to let LVM and
> my locigal volume to make use of this new disk size, and probably
> future disk size growth.
>
I've been doing this recently with VMWare ESX server. To save space, I 
create base disk images of clean OS installs on a minimalistic sized 
disk. If I need space, I use tools from VMWare to make the virtual disk 
bigger, and then grow the bits inside Linux with LVM.

I used the following two documents for info:
http://fedoranews.org/mediawiki/index.php/Expanding_Linux_Partitions_with_LVM
http://www.knoppix.net/wiki/LVM2

In my case, I was growing the root filesystem, so I needed to boot into 
something like Knoppix (hence the 2nd link above).

To summarize the links...(usual caveats, backup data, etc, etc)
-Create  a new partition of type 8e (Linux LVM) on the new empty space.

-Add that pv to LVM
 If the new partition is /dev/sda3, then this would look like
pvcreate /dev/sda3


-Extend the volume group that contains the logical volume you want to 
add this space to
 If the the VG is VolGroup00 then
vgextend VolGroup00 /dev/sda3

-Here I usually run vgdisplay, and get the amount of free disk space 
that now exists. (Look for the line that says Free PE / Size)
 If the Free PE / Size says there are 2.2GB free and the LV is LogVol00 
you could do
lvextend -L+2.2G /dev/VolGroup00/LogVol00

-Extend the filesystem. For ext2/ext3, use resize2fs (you may want to 
fsck before this, this is with the filesystem unmounted)
  resize2fs /dev/VolGroup00/LogVol00

-Fsck
 e2fsck -fy /dev/VolGroup00/LogVol00 (you may now want to use -y)

The trick I had when doing this in Knoppix for existing LVMs was after 
fdisk'ing to run vgscan; vgchange -a y to get the existing LVM 
partitions recognized and /dev entries created.

-Shawn