====== LVM - Logical volume manager ======

  * https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/logical_volume_manager_administration/index
  * https://wiki.archlinux.org/index.php/LVM
  * https://wiki.gentoo.org/wiki/LVM

  * List Physical Volumes: ''pvs''
  * List Volume Groups: ''vgs''
  * List Volumes: ''lvs''



<code>
pvcreate /dev/sdX
vgcreate vg0 /dev/sdX
</code>

===== Thin volumes =====

It's better to use thin provisioned volumes to have snapshots comes for free (copy on write) and are better for SSDs

Thin provisioned volumes are created from a "pool".

<code>
lvcreate -L 100G --thin vg/thin
</code>

Then create volume within the pool:

<code>
lvcreate -n myvol -T vg/thin -V 10G
</code>


Then to take a snapshot:

<code>
lvcreate -kn -n myvol_snap -s vg/myvol
</code>

To restore the snapshot

<code>
lvremove vg/myvol
lvrename vg/myvol_snap vg/myvol
</code>


==== Non-Thin volumes ====

Create a volume:

<code>
lvcreate -L10G -n myvol vg
</code>

Take a snapshot, you **MUST** give a size here, the diff between snapshot and original volume will be stored here. In case of this space being consumed, the snapshot is corrupted :/

<code>
lvcreate -L2G -s -n myvol_snap vg/myvol
</code>


To restore the snapshot

<code>
lvconvert --merge vg/myvol_snap
</code>


=== Backup using lvm snapshots ===

  * [[soft:burp|script for BURP backup program]]
  * http://ed.zehome.com/2018/sauvegarde-lvm-simple-partie-2/ backup block device limiting impact on CPU and disk I/O