I got it.

Today, oVirt supports importing ISO and Export Storage Domains, however, there is no support for importing an existing Data Storage Domain. A Data Storage Domain contains disks volumes and VMs/Templates OVF files. The OVF file is an XML standard representing the VM/Template configuration including disks, memory, CPU and more. Based on this information stored in the Storage Domain we can revive entities such as disks, VMs and Templates in the setup of any Data Center the Storage Domain will be attached to. The usability of the feature might be useful for various use cases, here are some of them:

Recover after the loss of the oVirt Engine’s database.
Transfer VMs between setups without the need to copy the data into and out of the export domain.
Support migrating Storage Domains between different oVirt installations.

Storage Domains that can be restored for VMs/Templates must contain OVF_STORE disks. Since OVF_STORE disk is only supported from a 3.5v Data Center, the Storage Domains that can be restored have to be managed in a 3.5v Data Center before the disaster. As long as the setup contains 3.5v Data Centers, the Import Storage Domain feature will automatically be supported for those Data Centers.

From: users-bounces@ovirt.org <users-bounces@ovirt.org> On Behalf Of Tommy Sway
Sent: Wednesday, September 22, 2021 6:48 PM
To: 'Vojtech Juranek' <vjuranek@redhat.com>; users@ovirt.org
Subject: [ovirt-users] Re: about the OVF_STORE and the xleases volume

Are you referring to the description of this passage?

Detailed Description

VM/Template configurations (including disks info) are stored on the master storage domain only for backup purposes and in order to provide the ability to run VMs without having a running engine/db. This feature aims to change the current place in which the OVFs are stored while using the existing OvfAutoUpdater feature (asynchronous incremental OVF updates). The expected benefits are:

Having “self contained” Storage Domains which will enable to recover in case of data loss (oVirt supports registration of unknown disks stored on storage domain in the engine and adding VM from OVF configuration - so having the VM OVF stored on the same Storage Domain of it’s disks will allow to recover the vm “completeness” from that Storage Domain to the oVirt engine).
Moving out from using the master_fs on the storage domain, as part of this change the OVFs will be stored on a designated volume located on each Storage Domain.
Adding support for streaming files from the engine to vdsm (will be discussed later on).

-----Original Message-----
From: Vojtech Juranek <vjuranek@redhat.com>
Sent: Wednesday, September 22, 2021 6:12 PM
To: users@ovirt.org
Cc: Tommy Sway <sz_cuitao@163.com>
Subject: Re: [ovirt-users] about the OVF_STORE and the xleases volume

On Wednesday, 22 September 2021 10:39:34 CEST Tommy Sway wrote:

> I wonder if the xleases volume mentioned here refers to ovf_store ?

No, xleases is part of the disk space used internally by oVirt (to manage concurrent access to the resources, e.g. disk image) and shouldn't be touched by the user.

OVF store is Open Virtualization Format [1] and it's used for storing these files, see [2] for more details.

[1] https://en.wikipedia.org/wiki/Open_Virtualization_Format

[2] https://www.ovirt.org/develop/release-management/features/storage/

importstoragedomain.html

> * A new xleases volume to support VM leases - this feature adds the

> ability to acquire a lease per virtual machine on shared storage

> without attaching the lease to a virtual machine disk.

> A VM lease offers two important capabilities:

> * Avoiding split-brain.

> * Starting a VM on another host if the original host becomes

> non-responsive, which improves the availability of HA VMs.