[ovirt-users] Trying to understand the mixed storage configuration options.

[Pavel Gashev]

Nir,

Basically, almost any server has a local storage. It could be a reliable, RAID enabled storage. It would be great to allow to use it simultaneously with shared storages.

Other virtualizations like vmware/hyperv support local and shared storages simultaneously. If your VM is on local storage, it's tied to a host. Just like when VM has attached local device(s). VM migration moves disks between hosts as well.

An obvious solution is to export local storages via NFS to make it shared. This would allow to drop «local storage datacenters» as a class.

TODO list would be the following:
1. VDSM: add creating NFS exports
2. Engine: creating NFS exports before local storage activation, and updating NFS exports after adding/removing hosts
3. Engine: add moving disks between storages during (just before, just after) VM migration. 
4. Engine: add constraints to avoid dangerous situations - disallow changing VM startup host, disallow moving disks to another local storage without VM migration, etc.

On 13/05/16 14:04, "users-bounces at ovirt.org on behalf of Nir Soffer" <users-bounces at ovirt.org on behalf of nsoffer at redhat.com> wrote:

>On Thu, May 12, 2016 at 5:50 AM, Jason Ziemba <jason at ziemba.net> wrote:
>> I'm fairly new to oVirt (coming from ProxMox) and trying to wrap my head
>> around the mixed (local/NAS) data domain options that are available.
>>
>> I'm trying to configure a set of systems to have local storage, as their
>> primary data storage domain, though also want to have the ability to have a
>> NAS based data domain for guests that are 'mobile' between hosts.  Currently
>> I'm able to do one or the other, but not both (so it seems).
>>
>> When I put all of the systems in to a single cluster (or single data-center)
>> I'm able to have the shared data domain, though have only found the ability
>> to configure one system for local storage (not all of them).   When I split
>> them out in to separate data centers, they all have their local data domain
>> working, but only a single dc is able to access the shared data domain at a
>> time.
>>
>> Am I missing something along the way (probably fairly obvious) that does
>> exactly what I'm outlining, or is this functionality not available by
>> design?
>
>This is not available by design.
>
>Can you explain the use case, why do you need to use local storage as
>your primary data storage?
>
>How are you going to migrate your vms if the primary storage is local?
>
>How are you going to start the vms on another host after host failures,
>if the vm storage is on the failed host, and the last state of that disk
>is not available or even lost?
>
>Nir
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