[ovirt-users] Host non operationnal due to an iSCSI problem

[Alex Crow]

On 19/07/16 15:22, Alexis HAUSER wrote:
>> I'm still finding this hard to understand. If you are using iSCSI, you
>> /are/ using a server (called the "Target" in SCSI speak). Is the iSCSI
>> storage actually on the first host?
> It's a Dell bay (or "storage array", I think that's the correct name in english...)

If it offers iSCSI, it is indeed a "Target". It's effectively a server 
as it's offering up a service on the network! That does explain my 
confusion though...

>
>> How did you actually do the
>> discovery and assign the LUNs? In the storage domain properties you
>> should be able to see the IP and port of the Targets, something like
>> "iqn.2012-02:foo-target1,192.168.10.10,3260", and you need to ensure the
>> second host can reach that IP and port to be able to see the storage.
> Actually I jutt made a test : authorize access only to the second host (on the Dell bay), it works but only after setting it to maintenance mode and reactivate it.
> Then authorizing both of the hosts (as initially) make them both working now...It doesn't really makes sense...
> It is a very strange behavior. Maybe the second host needed to be set in maintenance mode then reactivated ?

Normally you should not have to do that. It could be that it was not 
allowed access, and you'd have to leave it a while for the host to retry.

At least you have it working now!

>
>
>
>> If you only have one physical interface on each host, there's not much
>> point doing multipath, as you don't stand to gain any performance or
>> resilience.
> I didn't choose if it was multipath or not, someone only gave me access to this storage, but I understand what you mean. However, I'll certainly add bonding later.
>
>
> Do you have any idea what setting maintenance mode and reactivating does on a host ? Does it restart some services ? I don't really understand what just happened actually...
> All I know is that it is used for backup, reinstall and update.

Maintenance mode will migrate any running VMs off that host and enable 
you to do some tasks (including the ones you mention) that you can't do 
when it's running VMs. I believe it stops certain services as well, not 
sure which ones. It's perfectly safe and routine thing to do in RHEV/oVirt.

Cheers

Alex


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