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From "Filip Hanik \(lists\)" <devli...@hanik.com>
Subject RE: questions of Cluster
Date Tue, 18 May 2004 02:10:09 GMT
>primary-secondary session replication
only replicate the session to one other machine

>if "Tomcat1" is crashed,only "Tomcat2"(if it's alive) can continue the
>services and replace "Tomcat1"

correct, if your system crashes two tomcats at a time, contact your system
administrator or debug your code :)
you would have the same problem in primary secondary if the primary and
secondary servers crashed at the same time

Filip


-----Original Message-----
From: 柴 小柴 [mailto:cqzfly@hotmail.com]
Sent: Friday, May 14, 2004 11:11 PM
To: tomcat-user@jakarta.apache.org
Subject: questions of Cluster


hello everyone! i have some questions:

Question 1
I have read this from tomcat-doc(5.0.24):
.............
For large clusters, the next release will support a primary-secondary
session replication
where the session will only be stored at one or maybe two backup servers
.............
Can you explain more about "primary-secondary session replication" and how
it works?
Thank you very much :)

Question 2
I have read this from tomcat-doc:
..............
In order to keep the network traffic down in an all-to-all environment,
you can split your cluster into smaller groups.
This can be easily achieved by using different multicast addresses for the
different groups.
A very simple setup would look like this:


         DNS Round Robin
               |
         Load Balancer
          /           \
      Cluster1      Cluster2
      /     \        /     \
  Tomcat1 Tomcat2  Tomcat3 Tomcat4
...............
Do you mean that:
if "Tomcat1" is crashed,only "Tomcat2"(if it's alive) can continue the
services and replace "Tomcat1",other instances in "Cluster2" can not do
that,
because different groups have different multicast addresses?
If my guess is true,i thank it may make a reduction in the capability of
"Cluster".
Am I correct?
Thank you for any comment!

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