Hello,

I did a test this morning attaching my NFS server as an export domain.  I shutdown the same 50Gb VM and exported it to the NFS export domain with oVirt GUI.  I surprisingly had very similar results to OVA exports, it took just about the same amount of time ~10 minutes, maybe even a tad longer (although I had more disk activity on the NFS server vs when I was doing OVA exporting). I would expect exporting as OVA would add some overhead with the loop device as well as performing a snapshot operation and whatever else it does (I don't know the inner workings of the scripts involved).

I'm not sure why your OVA export to direct attached NFS would be 20x slower than what I'm seeing in my environment. 

On Thu, Jan 23, 2020 at 2:49 AM Jürgen Walch <jwalch@plumsoft.de> wrote:
➢ I have a very similar setup as you and have just very recently started testing OVA exports for backup purposes to NFS attached storage.
➢ I have a three node HCI on GlusterFS (SSD backed) with 10Gbit and my ovirt management network is 10Gbit as well.  My NFS storage server is an 8 x 8Tb 7200 RPM drives in RAID10 running CentOS 8x with 10Gbit link.

Our setups are indeed similar, the main difference being, that my management network including the connection to the NFS server is only 1Gbit. Only GlusterFS has 10Gbit here.

➢ I haven't done specific measurement yet as I just setup the storage today but a test export of a 50Gb VM took just about ~10 minutes start to finish.

Doing the maths this is ~80MiB/s and 20 times faster than in my setup. Lucky you 😊
Much less than your 10Gbit link between NFS Server and nodes could provide, but maybe close to the limit of the drives in your NFS server.

The interesting thing is, that when setting up an export domain, stopping the VM and doing an export to the *same* NFS server, I'm getting write speeds as expected.
Only the OVA export is terribly slow.

The main difference I can see is the use of a loop device when exporting to OVA.
The export to the export domain does something like

        /usr/bin/qemu-img convert -p -t none -T none -f raw {source disk on GlusterFS} {target disk on NFS server}

whereas the OVA export will do

        /usr/bin/qemu-img convert -T none -O qcow2 {source snapshot on GlusterFS} /dev/loopX

with /dev/loopX pointing to the NFS OVA target image.

If you have the time and are willing to test, I would be interested in how fast your exports to an export domain are

--
       
     juergen

_______________________________________________
Users mailing list -- users@ovirt.org
To unsubscribe send an email to users-leave@ovirt.org
Privacy Statement: https://www.ovirt.org/site/privacy-policy/
oVirt Code of Conduct: https://www.ovirt.org/community/about/community-guidelines/
List Archives: https://lists.ovirt.org/archives/list/users@ovirt.org/message/FLQVWTKINNSGMIZVTNFIXOE2C4DF4VZ6/