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From aaron morton <aa...@thelastpickle.com>
Subject Re: Ec2Snitch to Ec2MultiRegionSnitch
Date Wed, 24 Apr 2013 03:33:36 GMT
> You are advising me to test it, what would be a good way of testing it (I can use AWS
EC2 instances if needed) ?
If you are only using one Available Zone per region then you have only one rack per DC and
the NetworkTopologyStrategy will do the right thing. 

> Why ? I mean we have maybe only 5% of our customers on the us-east zone, what in C* require
to have the same number of node on each DC ?
Because you are going to replicate your data 3 times in each DC so that each DC can operate
with a LOCAL_QUOURM. 

> What is better on adding nodes with no data and then rebuild them compared to using the
auto_bootstrap ?

nodetool rebuild is designed to handle pulling data from another dc, so you can use it when
the local DC does not contain data. i.e. you do not want a node in the new DC bootstrapping
from other nodes in the new DC, they have no data. 
  
> Any doc on this ? I am not aware of all the possibilities. Why is this the best method
according to you ?
http://wiki.apache.org/cassandra/Operations?highlight=%28token%29#Token_selection
http://www.datastax.com/docs/1.2/initialize/token_generation

Cause it's easier to understand than interleaving the nodes and works with 2+ DC's. 

> What is the point of this ?
http://wiki.apache.org/cassandra/FAQ#seed

> I didn't thought this change would be that tricky, thank you guys for these warnings
and your help ;)
Yup, this is a lot of work. 

Cheers
-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 23/04/2013, at 7:26 PM, Alain RODRIGUEZ <arodrime@gmail.com> wrote:

> Hi,these advice are very welcome.
> 
> @Dane, about the rack awareness, we use only one rack per DC, so I guess using EC2MultiRegionSnitch
will do just fine and it doesn't need any configuration. Does it seem right to you. If we
are someday interested on multi racks I will make sure to use them properly. Thank you for
this insight anyway. You are advising me to test it, what would be a good way of testing it
(I can use AWS EC2 instances if needed) ?
> 
> @Aaron
> 
> "I recommend using the same number of nodes in both DC's."
> 
> Why ? I mean we have maybe only 5% of our customers on the us-east zone, what in C* require
to have the same number of node on each DC ?
> 
> "Add the nodes (I recommend 6) with auto_bootstrap: false added to the yaml.
> update the keyspace replication strategy to add rf:3 for the new DC. 
> Use nodetool rebuild on the new nodes to rebuild them from the us-west DC. "
> 
> What is better on adding nodes with no data and then rebuild them compared to using the
auto_bootstrap ?
> 
> "I prefer to use the offset method. Take the 6 tokens from your us-west DC and add 100
to them for the new dc. "
> 
> Any doc on this ? I am not aware of all the possibilities. Why is this the best method
according to you ?
> 
> About seeds => "Yes. Have 3 from each."
> 
> What is the point of this ?
> 
> I didn't thought this change would be that tricky, thank you guys for these warnings
and your help ;)
> 
> Alain
> 
> 
> 2013/4/23 Dane Miller <dane@optimalsocial.com>
> On Thu, Apr 18, 2013 at 7:41 AM, Alain RODRIGUEZ <arodrime@gmail.com> wrote:
> > I am wondering about the process to grow from one data center to a few of
> > them. First thing is we use EC2Snitch for now. So I guess we have to switch
> > to Ec2MultiRegionSnitch.
> >
> > c/ I am using the SimpleStrategy. Is it worth it/mandatory to change this
> > strategy when using multiple DC ?
> 
> I suggest you thoroughly read the datastax documentation on cassandra
> replication.  The change you are planning is big - make sure to try it
> in a test environment first.  Also, you might find you don't really
> need Cassandra's rack aware feature, and can operate using
> (Gossiping)PropertyFileSnitch.  The rack feature is listed as an
> "anti-pattern" here:
> http://www.datastax.com/docs/1.2/cluster_architecture/anti_patterns
> 
> Here are some recent discussions on this list:
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/migrating-from-SimpleStrategy-to-NetworkTopologyStrategy-tp7586272.html
> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/migrating-from-SimpleStrategy-to-NetworkTopologyStrategy-tp7481090.html
> 
> Dane
> 


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