I think your are using an old version of OpenStack. I seem to remember a
discussion about a patch to remove the requirement of shared storage for
live migration on Ceph RBD. Are you using librbd in open stack?
Robert LeBlanc
Sent from a mobile device please excuse any typos.
On Apr 21, 2015 6:43 AM, "Neville" <neville.tay...@hotmail.co.uk> wrote:
> I'm trying to setup live migration in Openstack using Ceph RBD backed
> volumes. From what I understand I also need to put the libvirt folder
> /var/lib/nova/instances on shared storage for it to work as Nova tests for
> this as part of the migration process. I decided to look at using CephFS
> for this purpose.
>
> I've created a CephFS file system and mounted it on my two compute nodes
> as /var/lib/nova/instances but I'm getting some strange results. It seems
> like after one of the hosts accesses a file then it becomes locked and the
> other host can't access it. For example, I complete the following steps:
>
> 1\ Create new Openstack instance using the boot from image (create new
> volume) option. New instance is created with RBD backed volume as expected.
> On the relevant compute host I see the instance folder created under
> /var/lib/nova/instances/{*instance id}* with two files inside libvirt.xml
> and console.log. If I cat the libvirt.xml file it works as expected.
> 2\ Live migrate the instance to other host. Appears to work as expected
> although instance status in Horizon stays as migrating forever. I can see
> instance has moved to second host by running virsh list on both hosts.
> 4\ Now, if I attempt to cat the libvirt.xml file on the new host I get
> "Operation not permitted".
>
> I'm assuming this isn't what's expected?
>
> To test this further I tried the following basic tests:
>
> On Host 2:
>
> root@devops-kvm02:/var/lib/nova/instances# echo hello > test
> root@devops-kvm02:/var/lib/nova/instances# cat test
> hello
> root@devops-kvm02:/var/lib/nova/instances#
>
> Then from Host 1:
>
> root@devops-kvm01:/var/lib/nova/instances# cat test
> cat: test: Operation not permitted
> root@devops-kvm01:/var/lib/nova/instances#
>
> Then back on Host 2:
>
> root@devops-kvm02:/var/lib/nova/instances# cat test
> cat: test: Operation not permitted
> root@devops-kvm02:/var/lib/nova/instances#
>
> Should this even work? My understanding is CephFS allows concurrent access
> but I'm not sure if there is some file locking going on that I need to
> understand.
>
> Thanks,
>
> Neville
>
>
>
>
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>
>
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