[Linux-cluster] Basic Active Active File Server

Wed Jun 23 07:32:44 UTC 2010

Hey Jay,

I'm not at work at the moment, but this should get you started:

1/ The simplest test is to tell clustering to use broadcast instead of
multicast.
# In a single ESX server, you can use a host-only vSwitch for that.
# Disable multicast by removing the multicast reference from the cluster
configuration and restart the cluster

You can check multicast traffic between nodes in 2 ways:
2/ dumping packets
#relatively simple

tcpdump -i <interface> ip multicast
# I'm not sure (can't test from here), else try:
tcpdump -i <interface> ether multicast

# That should show multicast packets traveling over the interface to and
from the hosts and the multicast IP

3/ ping tests

# By enabling responses to broadcast pings in both Host O/S'es and pinging
them on their multicast address:
# http://kerneltrap.org/node/16225
echo "0" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

# find out the multicast IP of the cluster 
cman_tool status
# Ex: Multicast addresses: 239.192.12.239

# ping the multicast IP from each host
ping -L 239.192.12.239
#You should see ping replies.

About DNS:
Clustering will use the IP that the hostname resolves to.
The interface that IP resolves to will be used for multicast traffic.
If you need to use another interface, give the IP on that interface its own
hostname and put that in the cluster config.

About 224.0.0.1
I'm not sure, either.
I will try It out at the office.

Footnote:
http://sourceware.org/cluster/doc/usage.txt
Advanced Network Configuration
------------------------------

* UDP Port

CMAN uses UDP port 6809 by default.  A different port number can be used by:

<cman port="6809">
</cman>

* Multicast

CMAN can be configured to use multicast instead of broadcast (broadcast is
used by default if no multicast parameters are given.)  To configure
multicast
add one line under the <cman> section and another under the <clusternode>
section:

<cman>
    <multicast addr="224.0.0.1"/>
</cman>

<clusternode name="nd1">
    <multicast addr="224.0.0.1" interface="eth0"/>
</clusternode>

The multicast addresses must match and the address must be usable on the
interface name given for the node.

Regards,

Kit

-----Original Message-----
From: Jason Fitzpatrick [mailto:jayfitzpatrick at gmail.com] 
Sent: dinsdag 22 juni 2010 10:40
To: Kit Gerrits
Cc: linux clustering
Subject: Re: [Linux-cluster] Basic Active Active File Server

Hi Kit..

Awesome and all as I am when it comes to computers, networking is a serious
weak point ;0)

How would I go about checking if multicast traffic is making it between the
two nodes, they are now hosted of the same ESX server and therefore only
hitting the virtual switch in the ESX and should not have to traverse our
network at all.

I will review the ESX switch config and DNS (I have a horrible feeling that
the DNS gremlins are responsible, but am pretty sure that this should not
affect Multicast)

Also the multicast address that should be used, I am using 244.0.0.1
which I believe is 	The All Hosts multicast group that contains all
systems on the same network segment, but am not a 100% sure if this is the
correct setting.

Thanks again

Jay

On 22 June 2010 09:12, Kit Gerrits <kitgerrits at gmail.com> wrote:
>
> Keep in mind that multicast requires a multicast router to handle the 
> traffic.
> Mere Layer2 connectivity is not enough.
>
> If broadcast does work, that might be your problem.
>
> Kit
>
> -----Original Message-----
> From: linux-cluster-bounces at redhat.com 
> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Jason 
> Fitzpatrick
> Sent: maandag 21 juni 2010 18:14
> To: linux clustering
> Subject: Re: [Linux-cluster] Basic Active Active File Server
>
> Hi..
>
> I have tried both multicast and broadcast to no avail, as above I am 
> moving the systems to the same ESX to try and rule out the networking 
> end of things, I have not tried the tcpdump but was running wireshark 
> in an attempt to do the same as you recommended
>
> Jay
>
> On 21 June 2010 16:49, Kaloyan Kovachev <kkovachev at varna.net> wrote:
>> Hi,
>> On Mon, 21 Jun 2010 16:07:34 +0100, Jason Fitzpatrick 
>> <jayfitzpatrick at gmail.com> wrote:
>>> Hi all
>>>
>>> I am having no end of trouble getting a basic Active Active Cluster 
>>> working. at the moment it is in test / proof of concept and has 
>>> manual fencing in place but I cannot for the life of me get the 2 
>>> nodes to join to the one cluster (they both report joined in 
>>> crm_tool status but only to a local clustered instance if that makes 
>>> any
>>> sence)
>>>
>>> I have tried to use luci and system-config-cluster to get this up 
>>> and running and have been at it over a week, the network guys swear 
>>> that there is nothing blocking multicast traffic between them and 
>>> the firewalls have been disabled (they are on the same VLAN but 
>>> connected to different switches) servers have been rebuilt and have 
>>> RHEL 5.5 installed
>>>
>>
>> your problem is the multicast traffic - check with tcpdump if it is 
>> comming to the other server at all (network) and if it is, then 
>> doublecheck the firewall.
>> alternatively you may try using broadcast instead of multicast
>>
>>> Shared Storage is being provided by an Active Active DRBD setup 
>>> (tested and working)
>>>
>>> I have attached a copy of my cluster.conf
>>>
>>> Thanks in advance
>>>
>>> Jay
>>>
>>> --
>>>
>>> "The only difference between saints and sinners is that every saint 
>>> has a past while every sinner has a future. "
>>> - Oscar Wilde
>>
>> --
>> Linux-cluster mailing list
>> Linux-cluster at redhat.com
>> https://www.redhat.com/mailman/listinfo/linux-cluster
>
>
>
> --
>
> "The only difference between saints and sinners is that every saint 
> has a past while every sinner has a future. "
> - Oscar Wilde
>
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"The only difference between saints and sinners is that every saint has a
past while every sinner has a future. "
- Oscar Wilde
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