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Re: DRBD? [message #4880 is a reply to message #4875]

Tue, 01 August 2006 12:40

cdevidal
Messages: 24
Registered: June 2006
Location: Jacksonville, FL

Junior Member

wfischer wrote on Tue, 01 August 2006 04:24

The second reason is that in a active-passive configuration you can get aware of performance bottlenecks soon enough. We had a for example a cluster running, that ran Apache on node1 and MySQL on node2 (without any virtualization). When we started the project, every machine had 1,5 GB RAM. Apache needed about 500 MB, and also MySQL needed about 500 MB. After some time we discovered that Apache now needs 1 GB, and also MySQL consumes 1 GB of RAM - so if a failover would have happened the remaining cluster node would have started swapping and get very slow (in fact so slow, that it would have seemed that the cluster is down)
When you run all services on only one node, you can sooner discover those performance bottlenecks (actually before a failover happens) - and enlarge e.g. RAM like in this case.
Evan Marcus and Hal Stern have a very interesting discussion about why to use active/passive and what to answer to management when they ask: "how can I use the standby server?"

I'm glad I talked to someone with experience Wink

Good info, thank you.

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

R U good enough?
TenThousandDollarOffer.com

[Updated on: Tue, 01 August 2006 12:56]

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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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