Hello,
we are using oVirt on a production system with a three node
hyperconverged-cluster based on GlusterFS with a 10Gbit storage backbone
network.
Everything runs smooth except OVA exports.
Each node has a NFS mount mounted on
/data/ova
with custom mount option "soft".
The NFS server used is a plain vanilla CentOS7 host with /etc/exports
containing a line
/data/ova *(rw,all_squash,anonuid=36,anongid=36)
When exporting VM's as OVA using the engine web gui, the export is terribly
slow (~4MiB/s), it succeeds for small disks (up to 20GB), exporting larger
disks fails with a timeout.
The network link between oVirt-nodes and NFS server is 1Gbit.
I have done a little testing and looked at the code in
/usr/share/ovirt-engine/playbooks/roles/ovirt-ova-pack/files/pack_ova.py.
It seems, the export is done by setting up a loop device /dev/loopX on the
exporting node linked to a freshly generated sparse file /data/ova/{vmname}.tmp
on the NFS share and then exporting the disk using qemu-img with target
/dev/loopX.
Using iotop on the node doing the export I can see write rates ranging from 2-5
Mib/s on the /dev/loopX device.
When copying to the NFS share /data/ova using dd or qemu-img *directly* (that
is using /data/ova/test.img instead of the loop device as target) I am getting
write rates of ~100MiB/s which is the expected performance of the NFS servers
underlying harddisk-system and the network connection. It seems that the loop
device is the bottleneck.
So far I have been playing with NFS mount options and the options passed to
qemu-img in
/usr/share/ovirt-engine/playbooks/roles/ovirt-ova-pack/files/pack_ova.py
without any success.
Any ideas or anyone with similar problems ? 😊
--
juergen walch
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