[DRBD-user] Adding a third node

[Paul O'Rorke]

Thanks for that Aaron,

I'm looking at this page 
http://www.drbd.org/users-guide/s-three-nodes.html and not quite sure I 
understand how to merge this with my current config.  Currently I have 5 
resources using Protocol C on my 2 node local cluster.

For the sake of this set up I will consider the set up one of these 
resources with a third node using a stacked resource and protocol A then 
hopefully once that is working I can apply this to the other resources.

In the example provided it appears that I need to define all three 
resources in the one .res file.  I have the following 2 config files:

*/etc/drbd.d/global_common.conf*
global {
         usage-count yes;
}
common {
         protocol C;
}

and

*/etc/drbd.d/restored.res*
resource restored {
         device    /dev/drbd2;
         disk        /dev/VirtualMachines/restored;
         meta-disk internal;
         on kvm-srv-01 {
             address 192.168.2.41:7789;
         }
         on kvm-srv-02 {
             address 192.168.2.42:7789;
         }
}


can I just tack something like this onto the end of 
*/etc/drbd.d/restored.res*?

resource restored-U {
   net {
     protocol A;
   }

   stacked-on-top-of restored {
     device     /dev/drbd10;
     address    192.168.3.41:7788;
   }

   on buckingham {
     device     /dev/drbd10;
     disk       /dev/hda6;
     address    <fixed IP at backup node>:7788; # Public IP of the backup node
     meta-disk  internal;
   }
}


I am also wondering, since I have a spare NIC on my local nodes, would I 
be better to use that to connect to my off site resource or use the LAN 
connected NIC?  In the example above I used a different subnet for the 
off site and called the off site machine 'buckingham'.

I hope my question makes sense, still finding my feet here.

Please and thanks

*Paul O’Rorke*
Tracker Software Products
paul at tracker-software.com <mailto:paul.ororke at tracker-software.com>

On 9/25/2013 2:21 PM, Aaron Johnson wrote:
> Yes you can add the stacked resource later, I have done this same thing several times now by making the the device slightly larger first and using internal metadata.
>
> Also I have a DR site using protocol C and pull-ahead enabled without using DRBD proxy.  The main site and DR site are connected via cable modem connections (10Mbit up/ 20 down both sides).  The only thing I have troubles with is if I need to add a large amount of data (50+ GB), which in my case is fairly rare (daily norm is ~2GB), then it can take days or weeks to sync up fully again.  Also I used truck-based updates for the initial setup of ~1TB to avoid having to pull all that over the internet link.
>
> Thanks,
> AJ
>
>> On Sep 25, 2013, at 7:54 AM, Lionel Sausin <ls at numerigraphe.com> wrote:
>>
>> Le 25/09/2013 08:10, roberto.fastec at gmail.com a écrit :
>>> The purpose you are talking about, sounds more as the purpose DRBD Proxy has been developed for
>>>
>>> www.linbit.com/en/products-and-services/drbd-proxy
>> Yes and no, my understanding is that DRBD-proxy lets your production cluster run faster than the connection speed by acting like a write cache.
>> But if I'm not mistaken you still need a stacked configuration for 3 node setups until v9.0 is released.
>> Someone please correct me if that's wrong of course.
>>
>> Lionel Sausin
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