[ClusterLabs] [pacemaker+ clvm] Cluster lvm must be active exclusively to create snapshot
su liu
liusu8788 at gmail.com
Mon Dec 5 22:34:54 EST 2016
lvscan result on compute1 node:
[root at compute1 ~]# lvscan
inactive
'/dev/cinder-volumes/volume-1b0ea468-37c8-4b47-a6fa-6cce65b068b5' [1.00
GiB] inherit
2016-12-06 11:32 GMT+08:00 su liu <liusu8788 at gmail.com>:
> Digimer, thank you very much!
>
> I do not need to have the data accessible on both nodes at once. I want to
> use the clvm+pacemaker+corosync in OpenStack Cinder.
>
> then only a VM need access the LV at once. But the Cinder service which
> runs on the controller node is responsible for snapshotting the LVs which
> are attaching on the VMs runs on other Compute nodes(such as compute1
> node).
>
> Need I active the LVs in *exclusively mode all the time? to supoort
> snapping it while attaching on the VM.*
>
> *The following is the result when execute lvscan command on compute1 node:*
>
>
>
>
>
>
>
>
>
> *[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------- 1.00gand on the controller node:[root at controller ~]# lvscan
> ACTIVE '/dev/cinder-volumes/volume-1b0ea468-37c8-4b47-a6fa-6cce65b068b5'
> [1.00 GiB] inheritthank you very much!*
>
>
> 2016-12-06 11:15 GMT+08:00 Digimer <lists at alteeve.ca>:
>
>> On 05/12/16 09:10 PM, su liu wrote:
>> > Thanks for your replay, This snapshot factor will seriously affect my
>> > application.
>>
>> Do you really need to have the data accessible on both nodes at once? To
>> do this requires a cluster file system as well, like gfs2. These all
>> require cluster locking (DLM) which is slow compared to normal file
>> systems. It also adds a lot of complexity.
>>
>> In my experience, most people who start thinking they want concurrent
>> access don't really need it, and that makes things a lot simpler.
>>
>> > then, because now I have not a stonith device and I want to verify the
>> > basic process of snapshot a clustered LV.
>>
>> Working stonith *is* part of basic process. It is integral to testing
>> failure and recovery. So it should be a high priority, even in a proof
>> of concept/test environment.
>>
>> > I have a more question:
>> >
>> > After I create a VG: cinder-volumes on controller node, I can see it
>> > throuth vgs command on both controller and compute
>> > 1 nodes. then i create a
>> > LV:volume-1b0ea468-37c8-4b47-a6fa-6cce65b068b5. Then I execute the lvs
>> > command on both nodes:
>> >
>> > [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 controller ~]#
>> > [root at controller ~]#
>> > [root at controller ~]#
>> > [root at controller ~]# ll /dev/cinder-volumes/
>> > total 0
>> > lrwxrwxrwx 1 root root 7 Dec 5 21:29
>> > volume-1b0ea468-37c8-4b47-a6fa-6cce65b068b5 -> ../dm-0
>> >
>> >
>> >
>> > [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
>> > [root at compute1 ~]#
>> > [root at compute1 ~]#
>> > [root at compute1 ~]# ll /dev/cinder-volumes
>> > ls: cannot access /dev/cinder-volumes: No such file or directory
>> > [root at compute1 ~]#
>> >
>> >
>> >
>> > But it seems that the LV can't be exist on the compute1 node. My
>> > question is that how to access the LV on the compute1 node?
>> >
>> > thanks very much!
>>
>> Do you see it after 'lvscan'? You should see it on both nodes at the
>> same time as soon as it is created, *if* things are working properly. It
>> is possible, without stonith, that they are not.
>>
>> Please configure and test stonith, and see if the problem remains. If it
>> does, tail the system logs on both nodes, create the LV on the
>> controller and report back what log messages show up.
>>
>> digimer
>>
>> >
>> > 2016-12-06 9:26 GMT+08:00 Digimer <lists at alteeve.ca
>> > <mailto:lists at alteeve.ca>>:
>> >
>> > 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
>> > Papers and Projects: https://alteeve.ca/w/
>> > What if the cure for cancer is trapped in the mind of a person
>> without
>> > access to education?
>> >
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>> >
>> >
>> >
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>>
>> --
>> Digimer
>> Papers and Projects: https://alteeve.ca/w/
>> What if the cure for cancer is trapped in the mind of a person without
>> access to education?
>>
>>
>> _______________________________________________
>> Users mailing list: Users at clusterlabs.org
>> http://lists.clusterlabs.org/mailman/listinfo/users
>>
>> Project Home: http://www.clusterlabs.org
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>>
>
>
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