[DRBD-user] can't mount on secondary node

Martin Gerhard Loschwitz martin.loschwitz at hastexo.com
Wed Feb 1 14:34:42 CET 2012


> On 02/01/2012 12:38 PM, Lawrence Strydom wrote:
> > Hi Felix.
> > 
> > My setup is, supposed to be, fairly straightforward.  Two web servers,
> > one in production and the second as a hot standby.
> > The problem comes in with availabillity of IP addresses though. These
> > are hosted servers and the hosting company won't provide more than one
> > Live IP per machine. This means I can't use a floating virtual IP which
> > fails over to the second node as that would require a third live IP.

> You could send node1's IP floating and remove node2's public IP. Add
> internal IPs to both machines, so the passive node is reachable by
> hopping through the one with the public IP.

> Unless, of course, there are network policies in place that forbid such
> shenanigans.

> > Instead the hosting company provides fail over of the real IP of the
> > primary server to the secondary server through their control panel.
> > Weird I know but I didn't choose them, just got given the job.  Ok so
> > now I need data to be synchronous over both servers in case of primary
> > node failure so dual primary would make sense as the IP fail over is
> > already taken care of and no further action will be required to make the
> > data available on the secondary node.

> Fair enough. So the answer would probably still be the same: Do use
> pacemaker. The easier way will be to just manage DRBD+Apache, or even
> DRBD only. However, the production node is selected independently from
> pacemaker, which makes for an odd (and error-prone) design.

Please note that there are other ISPs that do this as well, and there are
solutions for this in place. Like for Hetzner:

https://blog.kumina.nl/2011/03/hetzner-failover-ip-ocf-script-part-iii-when-http-attacks/

I've personally set this up already, and it did work nicely. Maybe they
can help you, too. Maybe you can adopt this to work for your provider.

> Otherwise, you can set up Pacemaker + Fencing + OCFS2 + Dual-Primary and
> get away without promotions. But it's more challenging.

NO. NO. NO. NOOOOOOOOOOO.
NO NO NO NO. NO. NO.

NOOOOOOOOOOOOOOOO.

http://www.youtube.com/watch?v=qFkjdNeMe3E#t=0m09s

I'll say it again: Every time somebody recommends to use Pacemaker with
OCFS2, god kills a kitten. So people, please please please only and 
really only recommend OCFS2 (or GFS) when there are good reasons for it.
All the little kittens that survive will be really thankful!

I hardly think that this is a valid OCFS2 usage scenario, quite frankly. 
No offense meant, but introducing another level of complexity in this 
setup won't do any good.

> HTH,
> Felix

Best regards
Martin

-- 
Martin Gerhard Loschwitz
Chief Brand Officer, Principal Consultant
hastexo Professional Services
http://www.hastexo.com/


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