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

[Wolfgang Link]

I think if somebody is interested on what this command do in detail
she/he will read the man.

In case "-largest-new=1" makes no sence to a person, who has no idea
what going on anyway.

On 06/29/2016 10:50 AM, Emmanuel Kasper wrote:
>>  
>> +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
> 
> 
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