Relation between heartbeat,openais,corosync

clusterfailoverheartbeathigh-availabilitylinux-ha

i am planning for high availability on lucid ubuntu, i started with drbd after a simple configuration on drbd I went to heartbeat and had a simple config on it too.

on drbd official site a document told me heartbeat is legacy and i should meet pacemaker instead as CRM.

on pacemaker related documents i understand heartbeat and OpenAis both are cluster infrastructures but openais is more preferred choosed by redhat too, so i went to openais and installed openais after searching with openais i understand that corosync is a project come from openais and it seem that corosync is used with ubuntu instead of openais.

and i want to configure corosync but no config is present where document declare!

1.could any body describe role of pacemaker in relation with openais,corosync ?

2.what's exactly preferred technology for high availability on ubuntu?

could you please give a step by step guide to set high availability on ubuntu?

thanks in advance.

Best Answer

well i reached answer on myself! clustering include two part:

1.cluster resource management

2.infrastructure with massaging layer

legacy heartbeat is broken into heartbeat message layer and pacemaker so pacemaker is CRM.

and we have two option on message layer:heartbeat,openais. openais/corosync is preferred as: http://comments.gmane.org/gmane.linux.highavailability.user/32355

There are, however, features in Pacemaker that require OpenAIS which will work only with Corosync, not Heartbeat. Those features are concerned with the distributed lock managers used by cLVM (but not regular LVM), GFS/GFS2, and OCFS2. If you need that functionality, you must select OpenAIS/Corosync. If you do not, you're free to choose.

as: http://www.clusterlabs.org/wiki/FAQ

Originally Corosync and OpenAIS were the same thing. Then they split into two parts... the core messaging and membership capabilities are now called Corosync, and OpenAIS retained the layer containing the implementation of the AIS standard.

Pacemaker itself only needs the Corosync piece in order to function, however some of the applications it can manage (such as OCFS2 and GFS2) require the OpenAIS layer as well.

so i went to openais/corosync and integrate it with pacemaker.

Related Solutions

Heartbeat vs UCarp

i assume you're interested in simple active-passive setup.

ucarp & heartbeat in such setup do pretty much the same thing. in essence - they run provided scripts when machine is elected to be master / hot-standby.

heartbeat might look much more complicated [ since it can help you autoamte drdb mounts, restarting multiple services etc ] but at the end - you can script all of this and let ucarp invoke it].

personally - i run heartbeat with single resource - that is script that does following:

[un]binds appropriate ip address
runs couple of arp-broadcasts
starts[stops] required services

my very simplistic setup [ heartbeat 2.1.3-6 under debian lenny ]: i have two servers:

ser0 [preferred active node] with permanently assigned 10.0.0.2/24 at eth0
ser0b [hot-standby node waiting to replace master] with permanently assigned 10.0.0.3/24 at eth0

'floating ip' - assigned to the active node is 10.0.1.1/24 assigned to eth1

in this case service that gets high availability is apache. i separately sync apache's configs and content that is served from ser0 to ser0b.

files below are identical on both machines with one marked exception:

/etc/ha.d/authkeys:

auth 1
1 md5 somethingrandom

/etc/ha.d/haresources

ser0 ha.sh

/etc/ha.d/ha.cf

keepalive 2
deadtime 10
udpport        694 
; below - address permanently assigned to the peer node . this is for master:
ucast eth1 10.0.0.3
; and on slave i have 
; ucast eth1 10.0.0.2
udp     eth0
logfacility     local0
auto_failback on

node    ser0
node    ser0b

/etc/init.d/ha.cf [ it can as well be in /etc/ha.d/resources.d/ha.cf ]

#!/bin/bash
case "$1" in
  start)
        ip link set dev eth1 up
        # bind 'floating' ip to the interface
        ip a a 10.0.1.1/24 dev eth1
        # you might want to add some route-changes here if needed
        /usr/lib/heartbeat/send_arp -r 10 eth1 10.0.0.1 auto 10.0.0.255 255.255.255.0
        # to make sure apache reloads it's config when machine becomes master
        /etc/init.d/apache2 restart
  ;;

  stop)
        # we are no longer active, un-bind 'floating' ip from the interface
        ip a d 10.0.1.1/24 dev eth1
        # you could stop it as well or just skip this step
        /etc/init.d/apache2 restart
  ;;
esac
exit 0

Which messaging layer to use, Heartbeat or Corosync

Ok seeing as how there's nothing but tumbleweeds gusting through this thread I went out a did the legwork myself. I've made the decision to go with Corosync for the following reasons:

Corosync is a newer project (based on openais) and seems to be the 'future' for messaging layers
Hearbeat looks like it will be maintained for quite a while longer but ultimately could be mothballed
Corosync supports a few more features in Pacemaker then Heartbeat does not, I'm undecided if these features will be needed on my current project but having the choice is nice.

The following discussions helped me make my decision:

http://www.gossamer-threads.com/lists/linuxha/pacemaker/71053

http://answerpot.com/showthread.php?124007-Heartbeat+vs+OpenAIS

Corosync site: http://corosync.github.io/corosync/

Heartbeat site: http://www.linux-ha.org/wiki/Main_Page

Best Answer

Related Solutions

Heartbeat vs UCarp

Which messaging layer to use, Heartbeat or Corosync

Related Topic