[ClusterLabs] corosync/pacemaker on ~100 nodes cluser

[Radoslaw Garbacz]

Hi,

Thank you for the advice. Indeed, seems like Pacemaker Remote will solve my
big cluster problem.

With regard to your questions about my current solution, I scale corosync
parameters based on the number of nodes, additionally modifying some of the
kernel network parameters. Tests I did let me select certain corosync
settings, which works, but are possibly not the best (cluster is quite slow
when reacting to some quorum related events).

The problem seems to be only related to cluster start, once running, any
operations such as node lost/reconnect, agents creation/start/stop work
well. Memory and network seems important with regard to the hardware.

Below are settings I used for my latest test (the largest working cluster I
tried):
* latest pacemaker/corosync
* 55 c3.4xlarge nodes (amazon cloud)
* 55 active nodes, 552 resources in a cluster
* kernel settings:
net.core.wmem_max=12582912
net.core.rmem_max=12582912
net.ipv4.tcp_rmem= 10240 87380 12582912
net.ipv4.tcp_wmem= 10240 87380 12582912
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_no_metrics_save = 1
net.core.netdev_max_backlog = 5000

* corosync settings:
token: 12000
consensus: 16000
join: 1500
send_join: 80
merge: 2000
downcheck: 2000
max_network_delay: 150 # for azure

Best regards,


On Tue, Aug 23, 2016 at 12:00 PM, Ken Gaillot <kgaillot at redhat.com> wrote:

> On 08/23/2016 11:46 AM, Klaus Wenninger wrote:
> > On 08/23/2016 06:26 PM, Radoslaw Garbacz wrote:
> >> Hi,
> >>
> >> I would like to ask for settings (and hardware requirements) to have
> >> corosync/pacemaker running on about 100 nodes cluster.
> > Actually I had thought that 16 would be the limit for full
> > pacemaker-cluster-nodes.
> > For larger deployments pacemaker-remote should be the way to go. Were
> > you speaking of a cluster with remote-nodes?
> >
> > Regards,
> > Klaus
> >>
> >> For now some nodes get totally frozen (high CPU, high network usage),
> >> so that even login is not possible. By manipulating
> >> corosync/pacemaker/kernel parameters I managed to run it on ~40 nodes
> >> cluster, but I am not sure which parameters are critical, how to make
> >> it more responsive and how to make the number of nodes even bigger.
>
> 16 is a practical limit without special hardware and tuning, so that's
> often what companies that offer support for clusters will accept.
>
> I know people have gone well higher than 16 with a lot of optimization,
> but I think somewhere between 32 and 64 corosync can't keep up with the
> messages. Your 40 nodes sounds about right. I'd be curious to hear what
> you had to do (with hardware, OS tuning, and corosync tuning) to get
> that far.
>
> As Klaus mentioned, Pacemaker Remote is the preferred way to go beyond
> that currently:
>
> http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-
> single/Pacemaker_Remote/index.html
>
> >> Thanks,
> >>
> >> --
> >> Best Regards,
> >>
> >> Radoslaw Garbacz
> >> XtremeData Incorporation
>
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-- 
Best Regards,

Radoslaw Garbacz
XtremeData Incorporation
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