Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
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 These users are using outdated software and get no bugfixes (with the exception of Novell's SLES 10 customers).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 -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 260 bytes Desc: OpenPGP digital signature URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20091117/bf54540a/attachment.pgp>