[Pacemaker] drbd-xen and fencing

[Vadym Chepkov]

On Nov 15, 2010, at 2:08 AM, Andrew Beekhof wrote:

> Don't use init.d/drbd, use the ocf script that comes with the drbd packages

Well, that doesn't help with live migration, unfortunately.

This is quote from /etc/xen/scripts/block-drbd

# This script will not load the DRBD kernel module for you, nor will
# it attach, detach, connect, or disconnect your resource. The init
# script distributed with DRBD will do that for you. Make sure it is
# started before attempting to start a DRBD-backed domU.


> 
> On Thu, Nov 11, 2010 at 2:19 PM, Vadym Chepkov <vchepkov at gmail.com> wrote:
>> Hi,
>> 
>> I posted a less elaborate version of this question to drbd mail-list, but,
>> unfortunately, didn't get a reply,
>> maybe audience of this list has more experience.
>> I am trying to make xen live migration to work reliably, but wasn't
>> successful so far.
>> Here is the problem.
>> In a cluster configuration I have two type of resources - file systems on
>> drbd, with explicit drbd resources configuration and
>> Xen resources with implicit, using drbd-xen block device helper. For the
>> former everything works great, but the latter doesn't work quite well.
>> In order for helper script to work, drbd module has to be loaded and
>> underlying resources up. So I have to start init.d/drbd script.
>> I can't make it an lsb cluster resource, because stop will be disastrous for
>> file system resources. Enable it in startup sequence breaks
>> /usr/lib/drbd/crm-unfence-peer.sh, because cluster stack is not completely
>> up by the time drbd script finishes, and there is no way to configure only
>> specific resources that need to be initialized.
>> Also, I can't find a way fence Xen resource. I tried fence-peer
>> "/usr/lib/drbd/crm-fence-peer.sh -i xen_vsvn",
>> where xen_svn is the name of Xen primitive, but it doesn't work,
>> so there is a danger of starting Xen VM on an out-of-date node. Then there
>> is no way of monitoring underlying drbd resources too.
>> I thought of adding underlying drbd resource explicitly in the cluster, but
>> I can't figure out what would be the configuration
>> for "this resource can be master on both nodes, but if just on one, it's
>> fine too".
>> allow-two-primaries has to be allowed for live migration and at the time of
>> migration resources are primary on both nodes, but when migration finishes,
>> it's again primary/slave. But if I configure drbd resource in the cluster
>> with meta master-max="2" master-node-max="1",
>> cluster insists on having them both primary all the time.
>> Hope I didn't bore you to death and there is an elegant solution for
>> this conundrum :)
>> Thank you,
>> Vadym
>> 
>> 
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>> 
>> 
> 
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