LVM - Logical Volume Management

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Overview

LVM stands for Logical Volume Manager. These pages describe LVM 2.

Tons of information is available in the LVM HOWTO

To display information about your LVM setup use:

  • pvscan to display physical volumes set up for LVM
  • vgscan to display volume groups defined on physical volumes
  • lvscan to display logical volumes defined in volume groups.

You create your filesystems in logical volumes.

Physical Volumes

server:# pvscan
  PV /dev/hdc3   VG VOL2   lvm2 [94.04 GB / 91.04 GB free]
  PV /dev/hda3   VG VOL1   lvm2 [94.04 GB / 94.04 GB free]
  PV /dev/md0    VG RAID   lvm2 [139.69 GB / 115.74 GB free]
  Total: 3 [327.76 GB] / in use: 3 [327.76 GB] / in no VG: 0 [0   ]
server:#

Here are 3 physical partitions:

  • /dev/hda3 for volume group VOL1
  • /dev/hdc3 for volume group VOL2
  • /dev/md0 for volume group RAID (on a RAID storage device)

Volume Groups

Physical volumes are assembled in volume groups.

Here 3 volume groups exist: RAID, VOL1, and VOL2.

server:# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "VOL2" using metadata type lvm2
  Found volume group "VOL1" using metadata type lvm2
  Found volume group "RAID" using metadata type lvm2
server:#

Logical Volumes

Logical Volumes contain your filesystems and are created in volume groups.

Here are the three volume groups shown using lvscan.

server:# lvscan
  ACTIVE            '/dev/VOL2/TMP' [3.00 GB] inherit
  ACTIVE            '/dev/RAID/HOME' [2.10 GB] inherit
  ACTIVE            '/dev/RAID/USR' [9.70 GB] inherit
  ACTIVE            '/dev/RAID/VAR' [10.00 GB] inherit
  ACTIVE            '/dev/RAID/USRLOCAL' [1.00 GB] inherit
  ACTIVE            '/dev/RAID/ROOT' [152.00 MB] inherit
  ACTIVE            '/dev/RAID/VS-SSH' [1.00 GB] inherit
server:#

Here are the logical volumes defined in the volume groups.

  • VOL1 is empty
  • VOL2 has
    • TMP for /tmp
  • RAID has
    • HOME for /home
    • USR for /usr
    • VAR for /var
    • USRLOCAL for /usr/local
    • ROOT for /
    • VS-SSH for a virtual server /var/lib/vservers/ssh

Author: Bernt Hansen

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