[ovirt-users] Adding FCP - Request for comments

Daniel Helgenberger daniel.helgenberger at m-box.de
Wed May 20 17:46:01 UTC 2015

On 20.05.2015 19:10, Fábio Coelho wrote:
Hello Fabio,
> Thoughts about Adding Storage Luns
> As I am new here, I would appreciate some advice about some actions that I
> intend to perform, please read.
> I have added a LUN to my cluster and, for that task, I had to restart every node
> of it. There was no LUNs before, multipathd was stopped and multipath.conf
> inexisted. I was able to log in and manually configure multipath.conf, a simple
> multipathd start was not enough.
In theory this should have been enough. What puzzles me: Until now 
host-deploy always activated multipathd and writes a multipath.conf.

Here I strongly recommend to blacklist everything and then only white 
listing your vendors. Otherwise your error logs fill up and you cannot 
connect any USB stick to the host any more ;)

Then, add RHEV PRIVATE to the second line otherwise it will be 
overwritten on every host deploy run.

blacklist {
         device {
                 vendor "*"
                 product "*"

After activating multipathd and editing multipath.conf to your needs you 
would actually need to run the 'multipath' command to create the paths. [1]

Sometimes you need to rescan the LUNs, though, esp. if you changed sizes 
after activating them.
> If this wasn't enough, my double NetAPP ( through an Hitachi ) provided me with
> a not so empty brand new LUN, and the task to add the FCP failed to point this.
> Trusting my double, I spent some precious time searching for different problems,
> until receiving some guidance and do a simple dd if=/dev/zero to the initial
> blocks of the LUN.
IMHO you need to initialize the lun with a partition table at least 
(parted). dd will do also.

> Consulting the documentation
> ( http://www.ovirt.org/OVirt_Administration_Guide#Adding_FCP_Storage ) for this
> matters, was not of any help.
> So, my questions:
> This is the intended behavior? Should I open a ticket?
> Should I add a note to documentation to point such behavior? ( i'm about to )
I think this is not ovirts part but rather dm-multipath. My best guess 
would be a configuration error on your part?

> Cheers,
> by qoelheX
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Daniel Helgenberger
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