Create Logical Volume Manager (LVM) in Linux

In Linux, Logical Volume Manager (LVM) is a device mapper framework that provides logical volume management for the Linux kernel. Most modern Linux distributions are LVM-aware to the point of being able to have their root file systems on a logical volume. Heinz Mauelshagen wrote the original LVM code in 1998 (Source: wiki)

Advantages of LVM: (Source: wiki)

• Volume groups (VGs) can be resized online by absorbing new physical volumes (PVs) or ejecting existing ones.
• Logical volumes (LVs) can be resized online by concatenating extents onto them or truncating extents from them.
• LVs can be moved between PVs.
• Creation of read-only snapshots of logical volumes (LVM1), leveraging a copy on write (CoW) feature, or read/write snapshots (LVM2)
• VGs can be split or merged in situ as long as no LVs span the split. This can be useful when migrating whole LVs to or from offline storage.
• LVM objects can be tagged for administrative convenience.
• VGs and LVs can be made active as the underlying devices become available through use of the lvmetad daemon

LVM Elements: (Source: wiki)

Physical volumes (pv) are regular storage devices. LVM writes a header to the device to allocate it for management.

Volume Groups (vg) is the combination of physical volumes into storage pools known as volume groups.

Logical Volumes (lv) is the sliced portion of volume group

Create LVM:

Usually fdisk is used for drives that are smaller than 2TB and either parted or gdisk is used for disks that are lasger than 2TB. Here is a very good article that covers the differences, titled: The Differences Between MBR and GPT.

Find out the harddisk:

server1:~# fdisk -l

As there is no partitions yet on /dev/sdb, let's create a partition on it and assume the harddisk is larger than 2TB, we will use parted tool

parted /dev/sdb

(parted) mklabel gpt

(parted) unit TB

(parted) print

(parted) mkpart

Partition type?  primary/extended? primary

File system type?  [ext2]? xfs # other known filesystems are ext3, ext4

Start? 0

End? 11TB

(parted) print # print newly created disk

(parted) quit

Now check the changes again:

server1:~# fdisk -l

Now create PV, VG and LV. Once this is done, format the partition in desired partition type and mount the volume in under a mount point. For persistent, update fstab file accordingly.

server1:~# pvcreate /dev/sdb1        # create physical volume

server1:~# pvs                         # view physical volume

server1:~# vgcreate vg_data /dev/sdb1  # create volume group

server1:~# vgs                         # view volume group

server1:~# vgdisplay -v vg_data        # display volume group details with FREE PE (Physical Extent) number

server1:~# lvcreate -l +2621437 -n lv_data vg_data    # create logical volume group with FREE Physical Entent (PE) number

server1:~# vgdisplay -v vg_data        # view the volume group

server1:~# lvs                         # view the logical volume

server1:~# mkfs.ext4 /dev/vg_data/lv_data # format partition with ext4

OR

server1:~# mkfs.xfs /dev/vg_data/lv_data # format partition with xfs

server1:~# mkdir /data     # create a mount point

server1:~# mount /dev/vg_data/lv_data /data/ # mount newly created partition

server1:~# df -Th

server1:~# vim /etc/fstab

/dev/vg_data/lv_data /data/ default 0 0 # add fstab entry for a persistent automount after reboot, first 0 option is for skip backup and second 0 option is for no filesystem check (fsck) at boot time

Let's assume the harddisk /dev/sdb is < 2TB. So for this, we will use fdisk instead of parted

server1:~# fdisk -l

server1:~# fdisk /dev/sdb

server1:~# fdisk> m # for help

fdisk> n # create new partition

fdisk> Primary/ Extended? Primary

fdisk> Partition ID: 1

fdisk> Start: [enter for default]

fdisk> End: [enter for default]

fdisk> p       # print newly created partition

fdisk> t                              # change the partition ID

fdisk> L [Print all types]       # change the partition ID

fdisk> 8e           # 8e is the partition code for Linux LVM

fdisk> w       # write and exit

server1:~# fdisk -l

Repeat the same process again starting from creation of PV, VG and LV. Format the partition and mount as above process.

Cheers :-)