On Sat, Jul 2, 2022 at 9:40 AM wrote:
>
> Greetings,
>
> Is it possible with oVirt to import existing VMs where the underlying
> storage is on raw iSCSI luns and to keep them on those luns?
>
> The historical scenario is that we have Virtual farms in multiple sites
> managed by an ancient Orchestration tool that does not support modern OS's as
> the hypervisor.
> - In each site, there are clusters of hypervisors/Hosts that have visibility
> to the same iSCSI luns.
> - Each VM has it's own set of iscsi luns that are totally dedicated to that VM
> - Each VM is using LVM to manage the disk
> - Each Host has LVM filtering configured to NOT manage the VM's iscsi luns
> - The VMs can be live migrated from any Hypervisor within the cluster to any
> other Hypervisor in that same cluster
>
> We are attempting to bring this existing environment into oVirt without
> replacing the storage model.
> Is there any documentation that will serve as a guide for this scenario?
>
> In a lab environment, we have successfully
> - Added 2 hypervisors (hosts) and oVirt can see their VMs as
> external-ovtest1 and external-ovtest2
> - Removed the LVM filtering on the hosts
This should not be needed. The lvm filter ensure that the host can
manage only the
disks used by the host (for example for the boot disk). Other disks
(e.g. your LUNs)
are not managed by the host, but they are managed by oVirt.
> - Created a storage domain that is able to see the iscsi luns, but we have
> not yet done the 'add' of each lun
Don't create a storage domain, since you want to use the LUNs directly.
Adding the LUNs to the storage domain can destroy the data on the LUN.
> Is it possible to import these luns as raw block devices without LVM being
> layered on top of them?
Yes, this is called Direct LUN in oVirt.
> Is it required to actually import the luns into a storage domain, or can the
> VM's still be imported if all luns are visible on all hosts in the cluster?
There is no way to import the VM as is, but you can recreate the VM
with the same LUNs.
> In the grand scheme of things, are we trying to do something that is not
> possible with oVirt?
> If it is possible, we would greatly appreciate tips, pointers, links to docs
> etc that will help us migrate this environment to oVirt.
You can do this:
1. Connect to the storage server with the relevant LUNs. The LUNs used by
the VM should be visible in engine UI (New storage domain dialog).
2. Create a new VM using the same configuration you had in the original VM
3. Attach the right LUNs to the VM (using Direct LUN)
4. In the VM, make sure you use the right disks - the best way is to use:
/dev/disk/by-id/{virtaio}-{serial}
When {serial} is the disk UUID seen in engine UI for the direct LUN.
{virtaio} is correct if you connect the disks using virtio, if you use
virtio-scsi the string will be different.
You may also need to install extra components on the boot disk, like
qemu-guest-agent or virtio drivers.
Note that oVirt does not use the LUNs directly, but the multipath device on
top of the SCSI device. This should be transparent, but be prepared to see
/dev/mapper/{wwid} instead of /dev/sdXXX.
Nir
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