[Linux-HA] quorumd - is anyone using it?

[Atanas Dyulgerov]

 >-------- Оригинално писмо --------
 >От:  b52 at entrap.de
 >Относно: Re: [Linux-HA] quorumd - is anyone using it?
 >До: linux-ha at lists.linux-ha.org
 >Изпратено на: Събота, 2008, Март 1 13:30:28 EET
 >----------------------------------
 >
 >> Hi all,
 >>
 >> is anyone actually using the quorum daemon?
 >>
 >> My assessment seems to suggest that it is not workable in any scenario;
 >> but maybe I have missed something?
 >>
 >> If not and I'm right, I am afraid that users might actually deploy it,
 >> thinking it solves something and then be very upset when it fails under
 >> fire. Possibly, the prudent action at this time is to disable it from
 >> the package and build by default, until it is completed.
 >
 >I thought it is essential for any cluster with an even amount of nodes?
 >How would you decide DR in a split-brain condition of two nodes without a
 >quorum server? Is it possible?


Yes, is possible. If you have 2 nodes just join a third node to the cluster without running any resources on it. There you go you have quorum without quorum server.

I beleive the quorum server idea is not that simple to use it only when you have even number of nodes. Quorum server should be used in DR when you have 2 separate data centers. Quorum server must decide which site is down and grant quorum to the other one, even if it has less nodes.

Imagine you have 5 nodes cluster. 3 nodes in site A, 2 nodes in site B. Network between both sites is down so site A has majority quorum thus continue to run the service. But what happens if site A is down? Site B must takeover the sevice but it has not majoroty quorum - 2 nodes only!

Here comes the Quorum server. Site B contacts the quorum server (change in membership is detected). Quorum server has lost connection to the site A therefore it grants quorum to site B.

Unfortunatelly Quorum server does not work in 2.1.3. I hope it get fixed ASAP.

Regards,
Atanas


 >
 >Cheers,
 >Holger
 >
 >> Regards,
 >>     Lars
 >>
 >> --
 >> Teamlead Kernel, SuSE Labs, Research and Development
 >> SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nьrnberg)
 >> "Experience is the name everyone gives to their mistakes." -- Oscar Wilde
 >
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