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Re: DRBD? [message #4941 is a reply to message #4880]

Fri, 04 August 2006 09:55

wfischer
Messages: 38
Registered: November 2005
Location: Austria/Germany

Member

cdevidal wrote on Tue, 01 August 2006 14:40

1.) Did you actually perform a failover and observe it to be so slow because it was swapping?

Yes, I had one situation like that. As far as I remember I also saw a situation where the OOM killer finally got active, as also the sum of physical RAM+swap was not big enough.

cdevidal wrote on Tue, 01 August 2006 14:40

2.) So then am I to understand that in theory load balancing and high availability aren't in conflict but in practice they are? For example OpenSSI, which gives you high availability + load balancing, but if you just have two nodes and every service fails over to the first node it gets to be so slow you might as well not have anything at all.
In other words, are load balancing and high availability mutually exclusive not in theory but in practice, at least for two nodes?

I have no experience with OpenSSI - I only know that it provides a single system image across many machines. When you need load balancing (like a webserver farm), you also need two clustered load balancer boxes (otherwise the load balancer would be a single point of failure). So with load balancing you need at least four machines (two load balancers and two servers) to also get high availability.

Up untill now I have not implemented a load balancing cluster yet (I only took a deeper look on linux virtual server).

another info: I updated http://wiki.openvz.org/HA_cluster_with_DRBD_and_Heartbeat - I think it is complete now. I hope I have not overlooked errors in the document, as it is rather long meanwhile.

best wishes,
Werner

Werner Fischer, Developer of a Virtuozzo-out-of-the-box-cluster solution at Thomas-Krenn.AG

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[Message index]

		DRBD? By: cdevidal on Wed, 12 July 2006 21:02
		Re: DRBD? By: aistis on Thu, 13 July 2006 12:05
		Re: DRBD? By: cdevidal on Fri, 14 July 2006 12:44
		Re: DRBD? By: wfischer on Fri, 14 July 2006 13:10
		Re: DRBD? By: cdevidal on Fri, 14 July 2006 13:19
		Re: DRBD? By: cdevidal on Fri, 14 July 2006 13:27
		Re: DRBD? By: wfischer on Fri, 14 July 2006 13:44
		Re: DRBD? By: cdevidal on Fri, 14 July 2006 14:30
		Re: DRBD? By: wfischer on Fri, 14 July 2006 14:39
		Re: DRBD? By: cdevidal on Fri, 14 July 2006 14:46
		Re: DRBD? By: wfischer on Fri, 14 July 2006 15:06
		Re: DRBD? By: cdevidal on Fri, 14 July 2006 15:10
		Re: DRBD? By: wfischer on Wed, 26 July 2006 11:45
		Re: DRBD? By: wfischer on Sun, 30 July 2006 18:21
		Re: DRBD? By: cdevidal on Mon, 31 July 2006 17:39
		Re: DRBD? By: wfischer on Tue, 01 August 2006 08:24
		Re: DRBD? By: cdevidal on Tue, 01 August 2006 12:40
		Re: DRBD? By: wfischer on Fri, 04 August 2006 09:55
		Re: DRBD? By: cdevidal on Fri, 04 August 2006 10:25
		Re: DRBD? By: cdevidal on Sat, 05 August 2006 14:03
		Re: DRBD? By: jimcooncat on Wed, 30 August 2006 13:08
		Re: DRBD? By: wfischer on Thu, 13 July 2006 14:12
		Re: DRBD? By: cdevidal on Thu, 13 July 2006 21:05
		Re: DRBD? By: cdevidal on Fri, 14 July 2006 12:23

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