[ovirt-users] Network & local disk on same host, live storage migration

[Alexander Wels]

On Thursday, April 07, 2016 07:47:59 AM Matthew Bohnsack wrote:
> Hello.
> 
> I've been doing some experimentation with oVirt 3.6 and CentOS 7.2 hosts,
> and I have a few high level questions, related to what I've seen in my
> testing:
> 
> 1/ It seems that for a given host, it's impossible to have both a local
> storage domain and a shared storage domain such as NFS.  Is this correct?
> If so, is adding this capability on the roadmap somewhere?  I would really
> like to have the ability for a single host to simultaneously support both
> local and network disks.
> 

Storage is defined on a data center level, not on a host level, so you are 
correct you cannot have local storage and shared storage in the same data 
center.

> 2/ Does oVirt support any sort of live storage migration functionality?
> 

Yes, if you go to the disks main tab, you can select the disk you want to 
migrate and click 'move'. This will give you a dialog that allows you to 
select the target storage domain and profile.

>   2.A/ For example, say I have one host (host#1) with two separate NFS
> storage domains (NFS#1 and NFS#2).  In this case,  can a VM on host#1
> associated with NFS#1 be live migrated to NFS#2 storage?  Or can this sort
> of storage movement only be accomplished by a shutdown of the VM and an
> export/import/restart workflow?
> 
>   2.B/ Is the scenario described in 2.A possible across two different hosts
> that share both NFS storage domains?  That is, can a VM guest on
> host#1/NFS#1 be live migrated to host#2/NFS#2?
> 

See above answer, you can live migrate between storage domains, and since 
storage domains are at a data center level if both hosts are in the same data 
center, and both storage domains are in the same data center, you can live 
migrate the storage as well as the VMs. It will be 2 separate operations 
though.

> 3/ Let's says that you setup a host (host#1) with a shared storage domain
> (NFS#1) and a second host (host#2) with a local storage domain (local#2).
> If you wanted to move a VM from host#1/NFS#1 to host#2/local#2, how would
> you most easily accomplish this?  All I could come up with is: Add NFS
> export domain to host#1, turn VM on host#1 off, export VM, add NFS import
> domain to host#2, import VM, on host#2 onto local#2, turn VM on on host#2?
> 

Since these hosts cannot be in the same data center (cannot mix shared and 
local storage) that is the only option I know of for this particular scenario. 

> Thanks for your help,
> 
> -Matthew