[ClusterLabs] [pacemaker+ clvm] Cluster lvm must be active exclusively to create snapshot

[Digimer]

On 05/12/16 08:16 PM, su liu wrote:
> *Hi all,
> 
> *
> *I am new to pacemaker and I have some questions about the clvmd +
> pacemaker + corosync. I wish you could explain it for me if you are
> free. thank you very much!
> 
> *
> *I have 2 nodes and the pacemaker's status is as follows:*
> 
> [root at controller ~]# pcs status --full
> Cluster name: mycluster
> Last updated: Mon Dec  5 18:15:12 2016        Last change: Fri Dec  2
> 15:01:03 2016 by root via cibadmin on compute1
> Stack: corosync
> Current DC: compute1 (2) (version 1.1.13-10.el7_2.4-44eb2dd) - partition
> with quorum
> 2 nodes and 4 resources configured
> 
> Online: [ compute1 (2) controller (1) ]
> 
> Full list of resources:
> 
>  Clone Set: dlm-clone [dlm]
>      dlm    (ocf::pacemaker:controld):    Started compute1
>      dlm    (ocf::pacemaker:controld):    Started controller
>      Started: [ compute1 controller ]
>  Clone Set: clvmd-clone [clvmd]
>      clvmd    (ocf::heartbeat:clvm):    Started compute1
>      clvmd    (ocf::heartbeat:clvm):    Started controller
>      Started: [ compute1 controller ]
> 
> Node Attributes:
> * Node compute1 (2):
> * Node controller (1):
> 
> Migration Summary:
> * Node compute1 (2):
> * Node controller (1):
> 
> PCSD Status:
>   controller: Online
>   compute1: Online
> 
> Daemon Status:
>   corosync: active/disabled
>   pacemaker: active/disabled
>   pcsd: active/enabled
> *
> *

You need to configure and enable (and test!) stonith. This is doubly-so
with clustered LVM/shared storage.

> *I create a lvm on controller node and it can be seen on the compute1
> node immediately with 'lvs' command. but the lvm it not activate on
> compute1.
> 
> *
> *then i want to create a snapshot of the lvm, but failed with the error
> message:*
> 
> /### volume-4fad87bb-3d4c-4a96-bef1-8799980050d1 must be active
> exclusively to create snapshot ###
> 
> /
> *Can someone tell me how to snapshot a lvm in the cluster lvm
> environment？ thank you very much。*

This is how it works. You can't snapshot a clustered LV, as the error
indicates. The process is ACTIVE -> deactivate on all node -> set
exclusive on one node -> set it back to ACTIVE, then you can snapshot.

It's not very practical, unfortunately.

> Additional information:
> 
> [root at controller ~]# vgdisplay 
>   --- Volume group ---
>   VG Name               cinder-volumes
>   System ID             
>   Format                lvm2
>   Metadata Areas        1
>   Metadata Sequence No  19
>   VG Access             read/write
>   VG Status             resizable
>   Clustered             yes
>   Shared                no
>   MAX LV                0
>   Cur LV                1
>   Open LV               0
>   Max PV                0
>   Cur PV                1
>   Act PV                1
>   VG Size               1000.00 GiB
>   PE Size               4.00 MiB
>   Total PE              255999
>   Alloc PE / Size       256 / 1.00 GiB
>   Free  PE / Size       255743 / 999.00 GiB
>   VG UUID               aLamHi-mMcI-2NsC-Spjm-QWZr-MzHx-pPYSTt
> 
> [root at controller ~]# rpm -qa |grep pacem
> pacemaker-cli-1.1.13-10.el7_2.4.x86_64
> pacemaker-libs-1.1.13-10.el7_2.4.x86_64
> pacemaker-1.1.13-10.el7_2.4.x86_64
> pacemaker-cluster-libs-1.1.13-10.el7_2.4.x86_64
> 
> 
> [root at controller ~]# lvs
>   LV                                          VG             Attr      
> LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
>   volume-1b0ea468-37c8-4b47-a6fa-6cce65b068b5 cinder-volumes -wi-a-----
> 1.00g
> 
> 
> [root at compute1 ~]# lvs
>   LV                                          VG             Attr      
> LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
>   volume-1b0ea468-37c8-4b47-a6fa-6cce65b068b5 cinder-volumes -wi-------
> 1.00g
> 
> 
> thank you very much!
> 
> 
> 
> 
> 
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Digimer
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