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I'm a newbie to ovirt and i have some questions about nfs storage in ovirt, so where should iso and data domains be located? on the machine running ovirt engine or on a host? and when you add a storage on administration web portal what exactly happens? are these exports mounted on the machine running ovirt engine?

ahmedjaad
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The domains can be located anywhere. If you don't know how to set them up or need something fast, you have the option to create an ISO domain during the engine deployment on the same machine as the engine, but it's not mandatory.

I usually set up a separate host for NFS, and for data domains I prefer to use iSCSI or FC - to take advantage of the multipathing features NFS is a bit behind on as a protocol.

When you add a storage domain, you provide some details (IP, login details - depends on the protocol really), then one of the hosts will reach out to the IP or WWID, check it's accessibility, format it and prepare it for use by oVirt (create metadata). Once that is done, all the hosts in the datacentre will try to connect to the new storage domain as well, those that fail, will produce an alert and change status.

The engine does not need to reach anything but the hosts, all the storage, network and other operations are scheduled on the engine, and then delegated to the hosts for execution, so the engine itself only needs to talk to the hosts (vdsmd port 54321).

dyasny
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  • Thanks for your very well explained answer. so say i have two servers say server1 and server2, i want server1 to run ovirt-engine and server2 to be the host, iso and data domains should also be in server2, how do i achieve this? given ovirt engine is up and running and server2 has been added as a host on the ovirt engine. – ahmedjaad Jan 09 '17 at 17:41
  • well, this is not a best kind of scenario. You could simply build an NFS export of two on server2 and create the domains using the IP of that server, but you might as well just use local storage and be done. If this is going to be the entire setup, you're probably better off doing it this way, otherwise, I would recommend you have the storage on a separate box, a NAS maybe – dyasny Jan 09 '17 at 19:29
  • Thanks, one thing i did not mention, i need to use LVM logical volumes for storage, I've been advised to use iSCSI, i have put up a question about that, http://serverfault.com/questions/825623/how-to-add-lvm-logical-volume-data-domain-with-iscsi-as-storage-type-on-ovirt – ahmedjaad Jan 11 '17 at 15:58
  • If you use block storage - iscsi or FC, oVirt will utilise LVM to divide the provided LUNs into VM disk images. – dyasny Jan 11 '17 at 16:50