[ovirt-users] Adding FCP - Request for comments

[Daniel Helgenberger]

On 22.05.2015 21:08, Nir Soffer wrote:
> ----- Original Message -----
>> From: "Daniel Helgenberger" <daniel.helgenberger at m-box.de>
>> To: "Fábio Coelho" <fabio.coelho at jfsc.jus.br>, "users" <Users at ovirt.org>
>> Sent: Wednesday, May 20, 2015 8:46:01 PM
>> Subject: Re: [ovirt-users] Adding FCP - Request for comments
>>
>>
>>
>> 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.
>> # RHEV PRIVATE
>>
>> blacklist {
>>           device {
>>                   vendor "*"
>>                   product "*"
>>           }
>> }
>
> This is bad idea. If you want to blacklist all devices, you can add this to
> vdsm generated configuration.
What can I add?

>
> Vdsm is depending on the defaults set in the "defaults" section.

I just looked; seems to me this is the default part vdsm is needing?

defaults {
     polling_interval        5
     no_path_retry           fail
     user_friendly_names     no
     flush_on_last_del       yes
     fast_io_fail_tmo        5
     dev_loss_tmo            30
     max_fds                 4096
}

The problem is there is no blacklisting at all in the default 
multipath.conf - at least not in mine.

I know this is a hard thing to do for a general version of the file 
witch works for anyone. As for my part I have only very specific devices 
/ vendors I want to have in my multipah.conf; so I blacklist everything 
and later on add blacklist exceptions like:

blacklist_exceptions {
         device {
                 vendor  "IFT"
                 product "*"
         }
}

Witch IMHO is (was?) since best practice a long time ago when I created 
my configs.

>
>>
>>
>>
>> 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?
>>
>> [1]
>> https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html-single/DM_Multipath/#mpio_setup
>>>
>>> Cheers,
>>>
>>> by qoelheX
>>>
>>>
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>>>
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>>>
>>
>> --
>> Daniel Helgenberger
>> m box bewegtbild GmbH
>>
>> P: +49/30/2408781-22
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>>
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>> D-10115 BERLIN
>>
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>

-- 
Daniel Helgenberger
m box bewegtbild GmbH

P: +49/30/2408781-22
F: +49/30/2408781-10

ACKERSTR. 19
D-10115 BERLIN


www.m-box.de  www.monkeymen.tv

Geschäftsführer: Martin Retschitzegger / Michaela Göllner
Handeslregister: Amtsgericht Charlottenburg / HRB 112767