On Mon, Apr 12, 2021 at 9:05 PM Chris Adams <c...@cmadams.net> wrote:
>
> I have an oVirt 4.3 cluster, running in one location. I have to move it
> to another location. I've got a couple of 1G links between the sites,
> and that's enough bandwidth for this (at least temporarily), but... I
> have my iSCSI networks defined with a MTU of 9000, and it turns out the
> site-to-site links only allow 1500 (and these links are going away after
> this is done, so I don't think either carrier would be interested in
> changing things to support larger).
>
> Because of that, the storage won't connect up. I tried going "under the
> hood" and setting a firewalld rule to force the MSS to a smaller value,
> but that didn't seem to get it.
>
> What happens if I change the MTU of an active iSCSI network in oVirt? I
> could just go manually change it on each node's iSCSI interfaces, but
> I'm not sure if oVirt might change it back.
oVirt will not modify your setting, the only thing we set on the nodes are
node.startup and node.session.xxx:
200 def addIscsiNode(iface, target, credentials=None):
201 # There are 2 formats for an iSCSI node record. An old style
format where
202 # the path is /var/lib/iscsi/nodes/{target}/{portal} and a new
style format
203 # where the portal path is a directory containing a record file for each
204 # bounded iface. Explicitly specifying tpgt on iSCSI login
imposes creation
205 # of the node record in the new style format which enables to access a
206 # portal through multiple ifaces for multipathing.
207 with _iscsiadmTransactionLock:
208 iscsiadm.node_new(iface.name, target.address, target.iqn)
209 try:
210 if credentials is not None:
211 for key, value in credentials.getIscsiadmOptions():
212 key = "node.session." + key
213 iscsiadm.node_update(iface.name, target.address,
214 target.iqn, key, value)
215
216 setRpFilterIfNeeded(iface.netIfaceName, target.portal.hostname,
217 True)
218
219 iscsiadm.node_login(iface.name, target.address, target.iqn)
220
221 iscsiadm.node_update(iface.name, target.address, target.iqn,
222 "node.startup", "manual")
You can add more configuration here ^^^
223 except:
224 removeIscsiNode(iface, target)
225 raise
You can also modify the nodes outside of ovirt, but oVirt may remove the
iscsi nodes with your modifications. So I think modifying vdsm to do what
you want is your best choice.
If this works and can be useful to others, we can think how to make this more
generic, maybe adding some configuration that will be applied to all nodes.
> Also, I'm not sure what
> would happen to open iSCSI TCP connections (would they reduce
> gracefully).
Your vms are running on top of multipath, so even if the iscsi
connection was broken and recovered, the vm is protected from
the short outage.
You can try to ask about it in open-iscsi mailing list:
https://groups.google.com/g/open-iscsi
> Any other suggestions/tips/etc.? I'd like to make this as transparent
> as possible, so was hoping to live-migrate VMs and storage.
Ales may have more insight on the network side.
Nir
_______________________________________________
Users mailing list -- users@ovirt.org
To unsubscribe send an email to users-le...@ovirt.org
Privacy Statement: https://www.ovirt.org/privacy-policy.html
oVirt Code of Conduct:
https://www.ovirt.org/community/about/community-guidelines/
List Archives:
https://lists.ovirt.org/archives/list/users@ovirt.org/message/6I42P5RXUUJB6LGJWX4QBGESVC6AMV5W/
