[ovirt-users] Question on Datacenters / clusters / data domains

[Eduardo Mayoral]

Thank you very much, Mr Leviim!

This made things clear.

Eduardo Mayoral Jimeno (emayoral at arsys.es)
Administrador de sistemas. Departamento de Plataformas. Arsys internet.
+34 941 620 145 ext. 5153

On 28/08/17 11:14, Shani Leviim wrote:
> Hi Eduardo,
> Welcome aboard!
>
> First, you may find some relevant information in here:
> http://www.ovirt.org/documentation/admin-guide/administration-guide/
> <http://www.ovirt.org/documentation/admin-guide/administration-guide/> .
>
> Regarding your questions:
> * A data domain in an oVirt Data Center must be available to every
> Host on the Data Center: Am I right?
> Yes, you're right.
>
> * Can I manually migrate VMs between Datacenters?
> VM migration can't be performed between data canters, so you can't use
> the 'migrate VM' function.
> In order to "migrate" your VM between different data canters, you can
> use 'export' and 'import' functions and an 'export domain':
> By creating an export domain for one of your DC's (each DC can have up
> to one export domain), and exporting your VM to that storage domain,
> you can then detach the export domain from that DC and attach it to
> the other DC, and by importing there your VM you'll finish the
> transaction. 
>
> Another option is to detach the VM's storage domain from one DC and
> attach it the second one.
> That way you'll move the whole storage domain between your DCs. 
>
> If you have any further questions, don't hesitate to ask :)
>
> *Regards,
> *
> *Shani Leviim
> *
>
> On Thu, Aug 24, 2017 at 2:51 PM, Eduardo Mayoral <emayoral at arsys.es
> <mailto:emayoral at arsys.es>> wrote:
>
>     Hi,
>
>         First of all, sorry for the naive question, but I have not
>     been able
>     to find good guidance on the docs.
>
>         I come from the VMWare environment, now I am starting to migrate
>     some workload from VMWare to oVirt (v4.1.4 , CentOS 7.3 hosts).
>
>         In VMWare I am used to have one datacenter, several host clusters,
>     and a bunch of iSCSI Datastores, but we do not map every iSCSI
>     LUN/datastore to every host. Actually we used to do that, but we hit
>     limits on the number of iSCSI paths with our infrastructure.
>
>         Rather than that, we have groups of LUNs/Datastores mapped to the
>     ESXi hosts which form a given VMware cluster. Then we have a couple of
>     datastores mapped to every ESXi in the vmware datacenter, and we use
>     those to store the ISO images and as storage that we use when we
>     need to
>     migrate VMs between clusters for some reason.
>
>         Given the role of the Master data domain and the SPM in oVIrt
>     it is
>     my understanding that I cannot replicate this kind of setup in
>     oVirt: a
>     data domain in an oVirt Data Center must be available to every Host on
>     the Data Center: Am I right?
>
>         So, our current setup is still small, but I am concerned that
>     as it
>     grows, if I stay with one Datacenter, several clusters and a group of
>     data domains mapped to every host I may run again into problems
>     with the
>     number of iSCSI paths (the limit in VMWare was around 1024), it is
>     easy
>     to reach that limit as it is (number of hosts) * (number of LUNs) *
>     (number of paths/LUN).
>
>         If I split my setup in several datacenters controlled by a single
>     oVirt-engine in order to keep the number of iSCSI paths
>     reasonable. Can
>     I manually migrate VMs between Datacenters? I assume that in order
>     to do
>     that, those datacenters will need to share some data domain , Can this
>     be done? Maybe with NFS?
>
>         Thanks for your help!
>
>     --
>     Eduardo Mayoral Jimeno (emayoral at arsys.es <mailto:emayoral at arsys.es>)
>     Administrador de sistemas. Departamento de Plataformas. Arsys
>     internet.
>     +34 941 620 145 ext. 5153 <tel:%2B34%20941%20620%20145%20ext.%205153>
>
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