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From "Oscar Haeger" <oscar.hae...@sigma.se>
Subject SV: [users@httpd] Split-brain problem.
Date Tue, 08 Apr 2008 09:38:42 GMT
Hi.
Heartbeat is usually a private network between the nodes, used to send data about which nodes
are alive. You'll want a low latency network for this. Google for clusters and heartbeat and
you'll find lots of information I'm sure.
 
Clusters can be used as High-Availiblity where server B is indeed just a backup, but it can
also be used as High-Performance where two or more servers share the requests between them.
Obviously the performance will degrade if parts of that cluster goes down. So yes, B can both
be a backup and an equally performing server, depending on your setup.
 
I'm a bit out of my compentence area here as I haven't done webserver clustering, but I do
believe the general principle is about right. I'm sure someone on this list will correct me
where I'm wrong.
 
Cheers,
 
Oscar

________________________________

Från: Ch Praveena [mailto:ps050202@gmail.com]
Skickat: ti 2008-04-08 10:47
Till: users@httpd.apache.org
Ämne: Re: [users@httpd] Split-brain problem.


Thank you Oscar,

  As I am new to clustering Tomcat, Let me  know some information about Heartbeat too.. 

And according to your information, Is that Server B a backup for Server A(So that when A fails,
B attain its responsibilites) or an equally performing server with A.




2008/4/8 Oscar Haeger <oscar.haeger@sigma.se>:


	From my experience with clustering that is when the connection between parts of the clusters
are lost and they can't agree on which one is supposed to keep serving the data. The most
common way around it afaik is to have a priority and heartbeat between the nodes and allow
them to kill each other off (something like STONITH = Shoot The Other Node In The Head) or
similar.
	
	So, if we have two servers A and B and a heartbeat (with STONITH) between them and node A
misses a few heartbeats (perhaps a lockup, perhaps something else), then node B will reset
node A and take over that nodes capabilities.
	
	This is without reading about Terracotta so things might be different there, but that's the
split-brain problem from my experience.
	
	Hope this helps
	
	Cheers
	
	Oscar
	
	________________________________
	
	Från: Ch Praveena [mailto:ps050202@gmail.com]
	Skickat: ti 2008-04-08 09:30
	Till: users@httpd.apache.org
	Ämne: [users@httpd] Split-brain problem.
	



	Hi all,
	
	  While going on with Terracotta article,
	-- http://www.terracotta.org/confluence/display/explore/How+Terracotta+Works,
	For implementing application server clustering, I found this phrase, "Split-brain problem."..
	
	Please let me know about this in detail..
	
	
	
	Regards,
	
	Praveena Chalamcharla,
	Securview....
	

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-- 
Regards,

Praveena Chalamcharla,
Securview.... 

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