RE: [EXTERNAL] Migration a Keyspace from 3.0.X to 3.11.2 Cluster which already have keyspaces

["Durity, Sean R" <SE...@homedepot.com>]

The size of the data matters here. Copy to/from is ok if the data is a few million rows per table, but not billions. It is also relatively slow (but with small data or a decent outage window, it could be fine). If the data is large and the outage time matters, you may need custom code to read from one cluster and write to another. If this is DataStax, the dsbulk utility would be ideal.


Sean Durity
-----Original Message-----
From: slmnjobs - <sl...@gmail.com>
Sent: Sunday, December 1, 2019 4:41 AM
To: user@cassandra.apache.org
Subject: [EXTERNAL] Migration a Keyspace from 3.0.X to 3.11.2 Cluster which already have keyspaces

Hi everyone,

I have a question about migrate a keyspace another cluster. The main problem for us, our new cluster already have 2 keyspaces and we using it in production. Because of we don't sure how token ranges will be change, we would like the share our migration plan here and take back your comments.
 We have two Cassandra clusters which one of them:

CLUSTER-A :
- Cassandra version 3.0.10
- describe keyspace:
CREATE KEYSPACE mykeyspace WITH replication = {'class': 'NetworkTopologyStrategy', 'DC1': '3', 'DC2': '3', 'DC3': '1'}  AND durable_writes = true;
- DC1 : 6 nodes
- DC2 : 6 nodes
- DC3 : 1 node (backup node, have all data)

CLUSTER-B :
- Cassandra version 3.11.2- DC1 : 5 nodes
- DC2 : 5 nodes- DC3 : 1 node
- Already have 2 keyspaces and write/read traffic

We want to migrate a keyspace which on CLUSTER-A to CLUSTER-B. There're some solutions for restore or migrate a keyspace on a new cluster but I haven't seen any safety way about how we can migrate a keyspace on existing cluster which already have keyspaces.

Replication Factor won't change.
We think about two ways : one of them using sstableloader and other one using COPY TO/COPY FROM commands.

Our migration plan is:

- export of keyspace schema structure with DESC keyspace on CLUSTER-A
- create keyspace schema on CLUSTER-B
- disable writing traffic on application layer
- load data from CLUSTER-A, DC3 backup node (which have all data) to CLUSTER-B, DC1 with sstableloader or COPY command (each table wiil be copy one by one).
- update cluster IP addresses in application configuration
- enable writing traffic on application layer
So do you see any risk or any suggestion for this plan? Thanks a lot.

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