Logical Volume Management (LVM)

###Logical Volume Management (LVM)###

Features:

1. Ability to create volume sets and stripe sets

2. LVM masks the underlying physical technology

(ATA,ATAPI,IDE,SCSI,SATA,PATA,etc.)

3. LVM represents storage using a hierarchy:

a. Volume groups

a1. Physical volumes (/dev/sda2, /dev/sdb2, etc.)

b. Logical Volumes

b1. File systems

3. LVM physical volumes can be of various sizes

4. Ability to resize volumes on the fly

Note: Volume groups join: physical volumes (PVs) and Logical Volumes (LVs)

6 Steps to setup LVM:

1. Create LVM partitions via fdisk or parted

a. fdisk /dev/sda, /dev/sdb, /dev/sdc

b. n

c. p

d. +10G

e. t - change to type '8e' (LVM)

f. w

g. partprobe /dev/sda

2. Create Physical Volumes using 'pvcreate'

a. pvcreate /dev/sda3 /dev/sdb3 /dev/sdc3

3. Create Volume Groups using 'vgcreate'

a. vgcreate volgroup001 /dev/sda3 /dev/sdb3 /dev/sdc3

Note: Volume groups can be segmented into multiple logical volumes

4. Create one or more Logical Volumes

a. lvcreate -L 10GB -n logvolvar1 volgroup001

b. lvcreate -L 10GB -n logvolusr1 volgroup001

5. Create File system on logical volume(s)

a. mke2fs -j /dev/volgroup001/logvolvar1

b. mke2fs -j /dev/volgroup001/logvolusr1

6. Mount logical volume

a. mkdir /var1

b. mount /dev/volgroup001/logvolvar1 /var1

c. mkdir /usr1

d. mount /dev/volgroup001/logvolusr1 /usr1

Note: Be certain to update: /etc/fstab so that volumes are mounted when the system

reboots

3-tiers of LVM display commands include:

a. pvdisplay - physical volumes - represent raw LVM partitions

b. vgdisplay - volume groups - aggregate physical volumes

c. lvdisplay - logical volumes - file systems - mount here

Rename of Logical Volume:

1. lvrename volume_group_name old new - used to rename volumes

Task: Rename 'logvolvar1' to 'logvolopt1'

a. lvrename volgroup001 logvolvar1 logvolopt1

Note: LVM is updated immediately, even while volume is mounted

However, you must remount the logical volume to see the changes

b. umount /var1 && mount /dev/mapper/volgroup001-logvolopt1 /opt1

c. Update /etc/fstab

Remove Logical Volume:

Task: Remove 'logvolusr1' from the logical volume pool

a. umount /usr1

b. lvremove /dev/mapper/volgroup001-logvolusr1

c. use 'lvdisplay' to confirm removal

Resize Logical Volume:

Task: Grow (resize) 'logvolopt1' to 20GB

a. lvresize -L 20GB /dev/volgroup001/logvolopt1

b. lvdisplay - to confirm new size of logical volume

c. df -h - will still reveal the current size

d. Resize the file system to update the INODE table on the logical volume to

account for the new storage in 'logvolopt1'

'resize2fs -f -p /dev/volgroup001/logvolopt1'

Note: You may resize file systems online if the following are met:

1. 2.6x kernel series

2. MUST be formatted with ext3

Task: Shrink (resize) 'logvolopt1' to 15GB

a. lvresize -L 15GB /dev/volgroup001/logvolopt1

b. lvdisplay

c. df -h

d. resize2fs -f -p /dev/volgroup001/logvolopt1

Note: online shrinking is not supported

e. df -h

Note: Check disk utilization prior to shrinking to reduce the risk of losing data

LVM GUI Utility:

system-config-lvm