[Pacemaker] Question: How many nodes can join a cluster?

[Pavlos Parissis]

On 18 October 2010 11:13, Dan Frincu <dfrincu at streamwide.ro> wrote:

>  Pavlos Parissis wrote:
>
>
>
> On 18 October 2010 10:52, Florian Haas <florian.haas at linbit.com> wrote:
>
>> ----- Original Message -----
>> > From: "Andreas Vogelsang" <a.vogelsang at uni-muenster.de>
>> > To: pacemaker at oss.clusterlabs.org
>> > Sent: Monday, October 18, 2010 9:46:12 AM
>> > Subject: [Pacemaker] Question: How many nodes can join a cluster?
>> > Hello,
>> >
>> >
>> >
>> > I’m creating a presentation about a virtual Linux-HA Cluster. I just
>> > asked me how many nodes pacemaker can handle. Mr. Schwartzkopff wrote
>> > in his Book that Linux-HA version 2 can handle up to 16 Nodes. Is this
>> > also true for pacemaker?
>>
>
> I have been asked the same question and I said to them, let's say it is
> 126, what is the use of having 126 nodes in the cluster?
> Can someone imagine himself going through the logs to find why the
> resource-XXX failed while there are 200 resources?!!
>
> The only use of having 126 nodes is if you want to have HPC, but HPC is
> total different story than high available clusters.
> Even in N+N setup I would go with more than 4 or 6 nodes.
>
>
> My 2 cents,
> Pavlos
>
>
>  Actually, the syslog_facility in corosync.conf allows you to specify
> either a log file for each node in the cluster (locally), or setting up a
> remote syslog server. Either way, identifying the node by hostname or some
> other identifier should point out what is going on where. Granted, it's a
> large amount of data to process, therefore (such is the case with any large
> deployment) SNMP is a much better alternative for tracking issues, or (if
> you have _126_ times the same resource) adding some notification options to
> the RA might be a choice, such as SNMP trap, or even email.
>
> BTW, I'm also interested in this, I remember reading something about 64
> nodes, but I'd appreciate an official response.
>
> Have you ever done troubleshooting on a 4 node cluster at 01:00 night?
believe me it is not fun.

I don't say there are no use cases which require a lot of nodes, but I have
my doubts if there are a lot of use cases for High Available Clusters.
Adding without a second thought nodes and services increase complexity,
which is one of the main root cause of major problems.


Cheers,
Pavlos
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