Question
Cassandra - Multi Data Center configurations
Does 7.3.1 supports multi data center configurations or is it feasible only in 7.4 and later versions.
Also, is it feasible to manually configure the changes in 7.3.1 environment to support dual/multi data centers (or) functional changes are also required that are only present in 7.4 environment or later.
We have gone through below link and it says few of the multi data center issues are fixed in 7.4 version.
https://community1.pega.com/node/1616016
Also, can you clarify on the below queries ,
- Without DC awareness, is it feasible to do node repair
- What is the Consistency level to be configured
- Is it always required to define multiple racks?
- If we have replication factor as 3 and we have multiple data centres, what is the Replication factor that we need to configure on each data centre?
- In a multi data centre if one data centre is down, will it allow us to truncate the Cassandra table
Could you please clarify at the earliest.
***Moderator Edit-Vidyaranjan: Updated SR details***
Hi
Please see responses below from the Decisioning product team.
Does 7.3.1 supports multi data center configurations
Yes, with Hfix-41762 (Notes on adding a second DSM center have previously bee shared with you)
Without DC awareness, is it feasible to do node repair
— not sure what is the question about, I'd say yes —
What is the Consistency level to be configured
By default Pega use consistency level ONE, there is no need to modify it.
Is it always required to define multiple racks?
No.
If we have replication factor as 3 and we have multiple data centres, what is the Replication factor that we need to configure on each data centre?
When replication factor is set to 3 and instruction above is followed, it is set to 3 for each datacenter. If one needs to restrict a keyspace to only one datacenter, it can be set using prconfig: dnode/cassandra_local_datacenter_keyspaces. In 7.3.1 by default only ADM keyspace is set as local.
For more details around racks and replication, see https://docs.datastax.com/en/cassandra/3.0/cassandra/architecture/archDataDistributeReplication.html
In a multi data centre if one data centre is down, will it allow us to truncate the Cassandra table
No, the cluster needs to be in consistent state to truncate table.
Let me know if you have any queries or concerns.