[ovirt-users] Convert local storage domain to shared

[Yedidyah Bar David]

Hi Gianluca,

Thanks for another great post!

Any chance you'd like to convert it to a blog/article on ovirt.org?

On Fri, Dec 1, 2017 at 2:25 AM, Gianluca Cecchi
<gianluca.cecchi at gmail.com> wrote:
> On Wed, Nov 29, 2017 at 6:49 PM, Demeter Tibor <tdemeter at itsmart.hu> wrote:
>>
>> Hi,
>>
>> Yes, I understand what do you talk about. It isn't too safe..:(
>> We have terrabytes under that VM.
>> I could make a downtime at most for eight hours (maybe), but meanwhile I
>> have to copy 3 TB of vdisks. Firstly I need export (with a gigabit nic) to
>> export domain, and back under 10gbe nic.
>> I don't know how is enough this.
>>
>> Thanks
>>
>> Tibor
>
>
> Hi Tibor,
> I'm in shortage of time these days, but I have to admit your problem was so
> intriguing that I couldn't resist and I decided to try and reproduce it.
> All happened on my laptop with Fedora 26 (time to upgrade? not enough
> time... ;-)
>
> So this is the test environment of all vms inside virt-manager:
>
> 1) Create 3.5.6 environment
>
> - CentOS 6.6 VM (this was the iso I had at hand...) with hostname c6engine35
> where I installed oVirt 3.5.6 as engine
> - CentOS 6.6 VM with hostname c6rhv35 (sorry for the rhv in the name but
> these weeks I'm also working on it so it came out quite naturally...) were I
> installed the Hypervisor of 3.5.6 repo
>
> I created a local DC on top of a directory of the hypervisor (/ldomain)
> I created a CentOS 6.6 VM in this storage domain with a 4Gb disk
>
> 2) Detach the local domain from DC
>
> HERE YOUR THEORETICAL DOWNTIME BEGINS
>
> To do so I powered off the test VM and created a fake further local domain
> based on another directory of c6rhv35
> Then put into maintenance the local domain to be imported in 4.1
> The fake local domain becomes the master.
> Detach the local domain.
>
>
> 3) Create 4.1.7 environment (in your case it is already there..)
> - CentOS 7.4 VM with hostname c7engine41 where I installed oVirt 4.1.7 as
> engine
> - CentOS 7.4 VM with hostname c7rhv41 were I installed the Hypervisor of
> 4.1.7 repo
>
> I created a shared DC NFSDC with a cluster NFSCL
> To speed things I exported a directory from the engine and used it to create
> an NFS storage domain (DATANFS) for the 4.1 host and activated it
>
> 4) Shutdown 3.5 environment and start/configure the 3.5 hypervisor to export
> its previously local storage domain directory
>
> Start c6rhv35 in single user mode
> chkconfig service_name off
>
> for this service_name:
> ebtables ip6tables iptables libvirt-guests libvirtd momd numad sanlock
> supervdsmd vdsmd wdmd
>
> reboot
> create an entry in /etc/exports
>
> /ldomain c7rhv41.localdomain.local(rw)
>
> service nfs start
>
> set up accordingly the /etc/hosts of the servers involved so that all know
> all...
>
> 5) import domain in 4.1
> Select Storage -> Import domain and put
>
> c6rhv35.localdomain.local:/ldomain
>
> You will get a warning about it being already part of another DC:
> https://drive.google.com/file/d/1HjFZhW6fCkasPak0jQH5k49Bdsg1NLSN/view?usp=sharing
>
> Approve operation and you arrive here:
> https://drive.google.com/file/d/10d1ea0TbPCZhoaAf7br5IVqnvZx0LzSu/view?usp=sharing
>
> Activate the domain and you arrive here:
> https://drive.google.com/file/d/1-4sMfVVj5WyaglPI8zhWUsdJqkVkxzAT/view?usp=sharing
>
> Now you can proceed importing your VMs; in my case only the testvm
> Select he imported storage domain and then the "VM Import" tab; select the
> VM and "Import":
>
> https://drive.google.com/file/d/18yjPvoHjTw6mOhUrlHJ2RpsdPph4qBxL/view?usp=sharing
>
> https://drive.google.com/file/d/1CrCzVUYC3vI4aQ2ly83b3uAQ3QQh1xhm/view?usp=sharing
>
> Note that it is an immediate operation, and not depending on the size of the
> disks of the VM itself
> At the end you get your VM imported; here details:
>
> https://drive.google.com/file/d/1W00TpIKAQ7cWUit_tLIQkm30wj5j56AN/view?usp=sharing
> https://drive.google.com/file/d/1qq7sZV2vwapRRdjbi21Z43OOBM0m2NuY/view?usp=sharing
>
> While you import, you can then gradually start your VMs, so that your
> downtime becomes partial and not total
> https://drive.google.com/file/d/1kwrzSJBXISC0wBTtZIpdh3yJdA0g3G0A/view?usp=sharing
>
> When you have started all your imported VMs, YOUR THEORETICAL DOWNTIME ENDS
>
> Your VMS are now running on your old local storage, exported from your old
> 3.5 host to your new 4.1 hosts via NFS
>
> You can now execute live storage migration of your disks one by one to the
> desired 4.1 storage domain:
> https://drive.google.com/file/d/1p6OOgDBbOFFGgy3uuWT-V8VnCMaxk4iP/view?usp=sharing
>
> and at the end of the move
> https://drive.google.com/file/d/1dUuKQQxI0r4Bhz-N0TmRcsnjwQl1bwU6/view?usp=sharing
>
> Obviously there are many caveats in a real environment such as:
>
> - actual oVirt origin and target version could differ from mine and behavior
> be different
> - network visibility between the two oVirt environments
> - layout of the logical networks of the two oVirt environments: when you
> import you could need to change logical network and have conflicting MACS:
> in my test scenario it was all on ovirtmgmt with the same macs range
> - live storage migration of TB of disks.. not tested yet (by me at
> least)....
> - other things that don't come to mind right now....
>
> HIH,
> Gianluca
>
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-- 
Didi