Mailing List Archive: DRBD: Users

LINBIT getting involved in Heartbeat

Index | Next | Previous | View Threaded

romainchanu at gmail

Nov 16, 2009, 10:37 PM

Post #1 of 6 (1340 views)
Permalink

LINBIT getting involved in Heartbeat

Hi,

Regarding the announcement of LINBIT getting involved in Heartbeat (cf.
http://blogs.linbit.com/florian/2009/11/16/linbit-announces-stewardship-for-heartbeat-code-base/),
you recommend the use of Pacemaker over OpenAIS / Corosync since OpenAIS /
Corosync is still in development and apparently (cf. link above) has
currently some issues.

Could you tell us more about that?

I am a bit confused because the guys from Pacemaker recommend OpenAIS /
Corosync...

Cheers,

Romain

florian.haas at linbit

Nov 17, 2009, 12:19 AM

Post #2 of 6 (1268 views)
Permalink

Re: LINBIT getting involved in Heartbeat [In reply to]

On 11/17/2009 07:37 AM, Romain CHANU wrote:
> Hi,
>
> Regarding the announcement of LINBIT getting involved in Heartbeat (cf.
> http://blogs.linbit.com/florian/2009/11/16/linbit-announces-stewardship-for-heartbeat-code-base/),
> you recommend the use of Pacemaker over OpenAIS / Corosync since OpenAIS
> / Corosync is still in development and apparently (cf. link above) has
> currently some issues.

Pacemaker is a cluster resource manager.
Heartbeat is a cluster messaging layer.
OpenAIS/Corosync is a cluster messaging layer.

The two cluster messaging layers in the stack are interchangeable. The
cluster resource manager is not.

Thus, "recommending Pacemaker over OpenAIS / Corosync" (i.e., saying
Pacemaker is better than OpenAIS/Corosync) would be nonsense. We
recommend Pacemaker, and we are now offering our customers and users a
choice of cluster messaging layers.

> Could you tell us more about that?
>
> I am a bit confused because the guys from Pacemaker recommend OpenAIS /
> Corosync...

Yes, and as far as I can see that is due to two reasons:

1. Heartbeat, up to this point, had no one who stood up for the
responsibility of maintaining the existing code base.
2. Heartbeat has scalability issues with larger clusters (about 8 nodes
and above).

Issue #1 is now resolved. Issue #2 is irrelevant for 2-node clusters
(which, as per http://www.clusterlabs.org/wiki/UsagePoll, constitute the
vast majority of Pacemaker clusters out there).

In contrast, OpenAIS/Corosync has two issues which are likely to affect
specifically DRBD based 2-node clusters, and happen to be largely
irrelevant for larger or non DRBD based clusters:

- redundant rings are suffering from breakage;
- cluster messaging does not support unicast.

Plus, there is one significant issue which hurts all existing Heartbeat
2.1.x users, regardless of whether they use DRBD or not:

- there is no upgrade path from Heartbeat 2.1.x clusters to Pacemaker
with OpenAIS/Corosync.

There's a bunch of people out there currently stuck on Heartbeat 2.1.x
because, at least that's our impression, they are reluctant to switch
communication stacks (Heartbeat->OpenAIS/Corosync) and move to a more
advanced cluster resource manager (Pacemaker) at the same time. These
users are using outdated software and get no bugfixes (with the
exception of Novell's SLES 10 customers). A supported Heartbeat
messaging layer allows you to retain Heartbeat, while moving from the
built-in 2.1.x CRM to Pacemaker.

I hope this clarifies things.

Cheers,
Florian

Attachments:

signature.asc (0.25 KB)

nine at detonation

Nov 17, 2009, 12:47 AM

Post #3 of 6 (1288 views)
Permalink

Re: LINBIT getting involved in Heartbeat [In reply to]

On Tuesday, 17. November 2009, Florian Haas wrote:

> In contrast, OpenAIS/Corosync has two issues which are likely to affect
> specifically DRBD based 2-node clusters, and happen to be largely
> irrelevant for larger or non DRBD based clusters:
>
> - redundant rings are suffering from breakage;
> - cluster messaging does not support unicast.

Also it would seem that OpenAIS does not support serial links between nodes
which makes it a NOGO for me. After years of being indoctrinated (for example
by you :) that having several independent communication paths is mandatory, I
just cannot go back that easily.

Regards,
Stefan
_______________________________________________
drbd-user mailing list
drbd-user [at] lists
http://lists.linbit.com/mailman/listinfo/drbd-user

florian.haas at linbit

Nov 17, 2009, 2:51 AM

Post #4 of 6 (1264 views)
Permalink

Re: LINBIT getting involved in Heartbeat [In reply to]

On 2009-11-17 09:47, Stefan Seifert wrote:
> On Tuesday, 17. November 2009, Florian Haas wrote:
>
>> In contrast, OpenAIS/Corosync has two issues which are likely to affect
>> specifically DRBD based 2-node clusters, and happen to be largely
>> irrelevant for larger or non DRBD based clusters:
>>
>> - redundant rings are suffering from breakage;
>> - cluster messaging does not support unicast.
>
> Also it would seem that OpenAIS does not support serial links between nodes
> which makes it a NOGO for me. After years of being indoctrinated (for example
> by you :) that having several independent communication paths is mandatory, I
> just cannot go back that easily.

Yes, having several independent comm paths is a good idea, and as I said
OpenAIS/Corosync is currently lacking in that regard. However, we
definitely do advise *against* using serial links for cluster
communications, and have done so ever since we started recommending
using Heartbeat 2.x in CRM mode.

With Heartbeat and Pacemaker, just as with Heartbeat 2.x with built-in
CRM, don't use serial links. Use redundant network links. Serial links
will break once your CIB reaches a certain size, and the cluster manager
decides it must push a full CIB across the wire.

Cheers,
Florian

Attachments:

signature.asc (0.25 KB)

romainchanu at gmail

Nov 17, 2009, 4:05 AM

Post #5 of 6 (1270 views)
Permalink

Re: LINBIT getting involved in Heartbeat [In reply to]

Hi Florian,

My bad for my first email. I meant "You recommend the use of *Heartbeat*
over OpenAIS / Corosync" (combined with Pacemaker).

The explanations are quite clear :-)

I am working on a two-node cluster with DRBD, Pacemaker. I guess I will
follow your advices and go for Heartbeat as the messaging layer.

Thank you and I stay tuned for any updates from LINBIT regarding Heartbeat.

Cheers,

Romain

2009/11/17 Florian Haas <florian.haas [at] linbit>

> On 2009-11-17 09:47, Stefan Seifert wrote:
> > On Tuesday, 17. November 2009, Florian Haas wrote:
> >
> >> In contrast, OpenAIS/Corosync has two issues which are likely to affect
> >> specifically DRBD based 2-node clusters, and happen to be largely
> >> irrelevant for larger or non DRBD based clusters:
> >>
> >> - redundant rings are suffering from breakage;
> >> - cluster messaging does not support unicast.
> >
> > Also it would seem that OpenAIS does not support serial links between
> nodes
> > which makes it a NOGO for me. After years of being indoctrinated (for
> example
> > by you :) that having several independent communication paths is
> mandatory, I
> > just cannot go back that easily.
>
> Yes, having several independent comm paths is a good idea, and as I said
> OpenAIS/Corosync is currently lacking in that regard. However, we
> definitely do advise *against* using serial links for cluster
> communications, and have done so ever since we started recommending
> using Heartbeat 2.x in CRM mode.
>
> With Heartbeat and Pacemaker, just as with Heartbeat 2.x with built-in
> CRM, don't use serial links. Use redundant network links. Serial links
> will break once your CIB reaches a certain size, and the cluster manager
> decides it must push a full CIB across the wire.
>
> Cheers,
> Florian
>
>
> _______________________________________________
> drbd-user mailing list
> drbd-user [at] lists
> http://lists.linbit.com/mailman/listinfo/drbd-user
>
>

alanr at unix

Nov 17, 2009, 5:35 AM

Post #6 of 6 (1261 views)
Permalink

Re: LINBIT getting involved in Heartbeat [In reply to]

OpenAIS / Corosync is more than 10 times the code in Heartbeat's
communication layer, and it will likely take more than the relatively
short amount of time that OpenAIS has been in real production to get
it where Heartbeat is after more than 10 years and 100K servers in
production.

It's worth noting that the author of Pacemaker may have personal
reasons for recommending OpenAIS - his advocacy and adoption of
OpenAIS helped him to help change employers.

Quoting Romain CHANU <romainchanu [at] gmail>:

> Hi,
>
> Regarding the announcement of LINBIT getting involved in Heartbeat (cf.
> http://blogs.linbit.com/florian/2009/11/16/linbit-announces-stewardship-for-heartbeat-code-base/),
> you recommend the use of Pacemaker over OpenAIS / Corosync since OpenAIS /
> Corosync is still in development and apparently (cf. link above) has
> currently some issues.
>
> Could you tell us more about that?
>
> I am a bit confused because the guys from Pacemaker recommend OpenAIS /
> Corosync...
>
> Cheers,
>
> Romain
>

_______________________________________________
drbd-user mailing list
drbd-user [at] lists
http://lists.linbit.com/mailman/listinfo/drbd-user

Index | Next | Previous | View Threaded

Interested in having your list archived? Contact Gossamer Threads