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From Andras Szerdahelyi <andras.szerdahe...@ignitionone.com>
Subject Re: multiple Datacenter values in PropertyFileSnitch
Date Fri, 12 Apr 2013 07:33:23 GMT
I would replicate your different keyspaces to different DCs and scale those appropriately
So, for example, HighLoad KS replicates to really-huge-dc, which would have, 10 nodes, LowerLoad
KS replicates to smaller-dc with 5 nodes.
The idea is , you do not mix your different keyspaces in the same datacenter ( this is possible
with NetworkTopology ) or for redundancy/HA purposes you place a single replica in the other
keyspace's DC but you direct your applications to the "primary" DC of the keyspace, with LOCAL_QUORUM
or ONE reads.

Regards,
Andras

From: Matthias Zeilinger <Matthias.Zeilinger@bwinparty.com<mailto:Matthias.Zeilinger@bwinparty.com>>
Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
Date: Friday 12 April 2013 07:57
To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" <user@cassandra.apache.org<mailto:user@cassandra.apache.org>>
Subject: RE: multiple Datacenter values in PropertyFileSnitch

I´m using for each application it´s own keyspace.
What I want is to split up for different load patterns.
So that 2 apps with same and very high load pattern are not clashing.

For other load patterns I want to use another splitting.

Is there any best practice or should I scale out, so that the complete load can be distributed
to on all nodes?

Br,
Matthias Zeilinger
Production Operation – Shared Services

P: +43 (0) 50 858-31185
M: +43 (0) 664 85-34459
E: matthias.zeilinger@bwinparty.com<mailto:matthias.zeilinger@bwinparty.com>

bwin.party services (Austria) GmbH
Marxergasse 1B
A-1030 Vienna

www.bwinparty.com

From: aaron morton [mailto:aaron@thelastpickle.com]
Sent: Donnerstag, 11. April 2013 20:48
To: user@cassandra.apache.org<mailto:user@cassandra.apache.org>
Subject: Re: multiple Datacenter values in PropertyFileSnitch

A node can only exist in one DC and one rack.

Use different keyspaces as suggested.

Cheers

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

@aaronmorton
http://www.thelastpickle.com

On 12/04/2013, at 1:47 AM, Jabbar Azam <ajazam@gmail.com<mailto:ajazam@gmail.com>>
wrote:


Hello,

I'm not an expert but I don't think you can do what you want. The way to separate data for
applications on the same cluster is to use different tables for different applications or
use multiple keyspaces, a keyspace per application. The replication factor you specify for
each keyspace specifies how many copies of the data are stored in each datacenter.
You can't specify that data for a particular application is stored on a specific node, unless
that node is in its own cluster.
I think of a cassandra cluster as a shared resource where all the applications have access
to all the nodes in the cluster.


Thanks

Jabbar Azam

On 11 April 2013 14:13, Matthias Zeilinger <Matthias.Zeilinger@bwinparty.com<mailto:Matthias.Zeilinger@bwinparty.com>>
wrote:
Hi,

I would like to create big cluster for many applications.
Within this cluster I would like to separate the data for each application, which can be easily
done via different virtual datacenters and the correct replication strategy.
What I would like to know, if I can specify for 1 node multiple values in the PropertyFileSnitch
configuration, so that I can use 1 node for more applications?
For example:
6 nodes:
3 for App A
3 for App B
4 for App C

I want to have such a configuration:
Node 1 – DC-A& DC-C
Node 2 – DC-B & DC-C
Node 3 – DC-A & DC-C
Node 4 – DC-B & DC-C
Node 5 – DC-A
Node 6 – DC-B

Is this possible or does anyone have another solution for this?


Thx & br matthias



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