You simply need to create the iSCSI store as a Seperate LUN from NFS then migrate your NFS Hosted VM's to it. 

No procedure as it's a pretty straight forward operation, in your case the TrueNAS would have to have enough unassigned storage for the iSCSI lun. 


On Fri, Dec 3, 2021 at 1:14 PM David Johnson <djohnson@maxistechnology.com> wrote:
Hello braintrust,

My ovirt cluster is prone to hanging when it is put under a high IO load. In an earlier thread, someone determined that this is consistent across architectures and infrastructures when NFS is used for the backing datastore for the cluster.

I was able to see a huge improvement by switching putting an nVME drive in as the intent log cache on the NAS. But, alas, that appears to have only put off the reckoning, and the cluster locked up again when I doubled the IO workload.

Prior email chains to this list have established that the hang occurs because "something" in qemu throws the VM into PAUSE state instead of IOWAIT state when under load. Other emails I have viewed seem to point at NFS as the root cause, so a "least cost" suggestion is to migrate from NFS to iSCSI as backing storage.

Is there an existing procedure for migrating Ovirt VM storage from NFS to iSCSI?

Current architecture:
Ovirt engine 4.4.4.7-1.el8  on centos 8.x, on bare metal intel desktop
2 hosts 4.4.4.7-1.el8  on centos 8.x
TrueNAS Core 2020, with shares exposed as NFS
10 GBit dedicated storage Network


Thanks,

David Johnson


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