Logical Volume Management

[glennzo]

Is anyone familiar with LVM? I've spent the last day or 2 scouring the web for information because I want to learn how this works. What I can't find or don't understand (or just plain over looked) is info that outlines the steps one needs to take once you physically add a hard disk to the system. What's first and what's second? Partition? Volume Group? Logical Volumes? I'm thinking that I need to partition the disk first, add a Volume Group, add Logical Volumes and then bring this new disk "online". Any thoughts? Any good links?

[PilotJLR]

This KB may help:
http://kbase.redhat.com/faq/FAQ_43_1372.shtm

But what you said is correct... in a nutshell, think of LVM like this:

Partitions are marked as physical volumes with pvcreate.
Physical volumes can then be added into a volume group. Think of the volume group as a big pool of storage (e.g. physical volumes).
From this volume group, you can then create logical volumes, which are basically virtualized partitions.

So just make a series of normal partitions with fdisk, mark those partitions are LVM in fdisk, then run pvcreate, then vgcreate, then lvcreate, and then apply a filesystem!

Hope this helps.

[glennzo]

Thanks for the reply PilotJLR. So you think that I may be starting to get a grasp on this LVM concept? I'll have a look at the link you provided. Thank you.

[SlowJet]

If you use a whole disk it does NOT even need to be partitioned.
Here I use sdb and create a /svr and a /mnt/bkup and later take a snapshot and tar /svr to /mnt/bkup.

#pvcreate /dev/sdb

#vgcreate VolGroup2010 /dev/sdb
#vgchange -a y

#lvcreate --size 5G --name LogVol2010svr VolGroup2010
#lvcreate --size 8G --name LogVol2010bkup VolGroup2010
#mkfs.ext3 /dev/VolGroup2010/LogVol2010svr
#mkfs.ext3 /dev/mapper/VolGroup2010-LogVol2010bkup

#mkdir /svr
#mount /dev/mapper/VolGroup2010-LogVol2010svr /svr
#mkdir /mnt/bkup
#mount /dev/mapper/VolGroup2010-LogVol2010bkup /mnt/bkup

#lvcreate --size 1G --snapshot --name LogVol2010snapsvr /dev/mapper/VolGroup2010-LogVol2010svr

mkdir /mnt/snapsvr
#mount /dev/mapper/VolGroup2010-LogVol2010snapsvr /mnt/snapsvr

cd /mnt/bkup
#tar -cj -f mybacksvr20081014 /svr ...

#cd /
#umount /mnt/snapsvr
#lvremove /dev/mapper/VolGroup2010-LogVol2010snapsvr

#umount /mnt/bkup


SJ