[pve-devel] [PATCH] Add useful examples to lvm/lvmthin section.

[Emmanuel Kasper]

>  
> +Storage Layout
> +~~~~~~~~~~~~~~
> +
> +On a default installation {pve} will use lvm.
> +
> +The layout looks like followed.
> +
> +.Default LVM Layout.
> +[width="100%",options="header"]
> +|==============================================================================
> +|VG  |LV	   |Mountpoint		|Note
> +|pve |swap	   |			|will used as swap partition
> +|pve |root	   |/			|
> +|pve |data	   |/var/lib/vz/	|{pve} < 4.2
> +|pve |data	   |			|{pve} >= 4.2
> +|==============================================================================
> +
> +In {pve} 4.2 we changed the LV data to a thin pool to provide snapshots and native performance of the disk.
> +The /var/lib/vz is now included in the LV root.

maybe for clarity we could reword this as such:

For {pve} versions up to 4.1, the installer creates a Logical Volume
called 'data' which is mounted at /var/lib/vz
Starting from 4.2 the Logical Volume 'data' is a LVM thin volume, used
for block based storage of guest systems, and /var/lib/vz is simply a
directory on the root file system.

This makes clearer when pve 4.3 is released, that it follows the 4.2
partitioning scheme.


> +Create a Volume Group
> +~~~~~~~~~~~~~~~~~~~~~
> +
> +Let's assume we have a empty disk /dev/sdb, where we want to make a Volume Group named vmdata.
> +
> +First create a partition.
> +
> + # sgdisk -N 1 /dev/sdb



> + #pvcreate --metadatasize 250k -y -ff /dev/sdb1
> +
> + #vgcreate vmdata /dev/sdb1
> +

maybe for clarity we could generally use long options whenever we can,
so the end user has an idea what the command is  doing
I guess some people will copy/paste this anyway without understanding,
but we can give them a chance
redhat documentation is also using long options with commands in its
documentation:
ex
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/4/html/Cluster_Logical_Volume_Manager/persistent_numbers.html

so here we would have

sgdisk --largest-new=1 /dev/sdb

pvcreate --metadatasize 250k  /dev/sdb1

do we need -ff and -y here ?


>  ifdef::wiki[]
>  
>  See Also
> diff --git a/pve-storage-lvmthin.adoc b/pve-storage-lvmthin.adoc
> index 23a72ea..fa3a572 100644
> --- a/pve-storage-lvmthin.adoc
> +++ b/pve-storage-lvmthin.adoc
> @@ -76,6 +76,46 @@ List available LVM thin pools on volume group `pve`:
>  
>   # pvesm lvmthinscan pve
>  
> +Create a extra LV for /var/lib/vz
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +This can be easily done by create an new thin LV.
> +It is thin provision.
> +
> + # lvcreate -n <Name> -V <Size[M,G,T]> <VG>/<LVThin_pool>
> +
> +A real world example it looks like
> +
> + # lvcreate -n vz -V 10G pve/data
could be for instance
lvcreate --name vz --virtualsize 10G pve/data