In general, yes, Pacemaker is reliable. If your config is wrong, you may
still have an outage in the event of a failure.
That said, if you are a business and need support, you probably want to
use whatever clustering software ships with the distribution you use. I
belive SuSE uses pacemaker, but RedHat still uses rgmanager. Pacemaker
is tech preview in RHEL6 but will be mainline in 7. I believe RedHat
employ some core developers of pacemaker.
David
On 11/29/12 4:10 PM, Hermes Flying wrote:
Thank you for your help.
I take it that you are find Pacemaker reliable in your experience?
Should I look into it?
*From:* David Coulson <[email protected]>
*To:* Hermes Flying <[email protected]>
*Cc:* Baptiste <[email protected]>; "[email protected]"
<[email protected]>
*Sent:* Thursday, November 29, 2012 11:04 PM
*Subject:* Re: HAproxy and detect split-brain (network failures)
Again, you need to talk to the pacemaker people for actual clustering
information.
The ping was so a node could detect it lost upstream connectivity, and
move the VIP, otherwise the VIP may continue to run on a system which
does not have access to your network. This has nothing at all to do
with split brain.
If you want to deal with split brain, add a third node. Period. You
also want to have redundant heartbeat communication paths. You also
want STONITH/fencing so if one node detects the other is down it'll
power it off or crash it. I've not had issues with a two-node cluster
with two diverse backend communication links and fencing enabled.
David
On 11/29/12 3:58 PM, Hermes Flying wrote:
"You can have pacemaker ping an IP (gateway for example) and migrate
the VIP based on that"
How does this help for splitbrain?
If I understand what you say, pacemaker will ping an IP and if
successfull will assume that the other node has crashed. But what if
the other node hasn't and it is just their communication link that
failed? Won't both become primary?
How does the ping help?
*From:* David Coulson mailto:[email protected]
*To:* Hermes Flying mailto:[email protected]
*Cc:* Baptiste mailto:[email protected]; mailto:[email protected]
mailto:[email protected]
*Sent:* Thursday, November 29, 2012 10:26 PM
*Subject:* Re: HAproxy and detect split-brain (network failures)
On 11/29/12 3:11 PM, Hermes Flying wrote:
I see now!
One last question since you are using Pacemaker. Do you recommend it
for splitbrain so that I look into that direction?
Any two node cluster has risk of split brain. if you implement
fencing/STONITH, you are in a better place. If you have a third node,
that's even better, even if it does not actually run any services
beyond the cluster software
I mean when you say that pacemaker restart HAProxy, does it detect
network failures as well? Or only SW crashes?
I assume pacemaker will be aware of both HAProxy1 and HAProxy2 in my
described deployment
You can have pacemaker ping an IP (gateway for example) and migrate
the VIP based on that. In my config I have haproxy configured as a
cloned resource in pacemaker, so all nodes have the same pacemaker
config for haproxy and it keeps haproxy running on all nodes all of
the time.
