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From "Durity, Sean R" <SEAN_R_DUR...@homedepot.com>
Subject RE: [EXTERNAL] Migration a Keyspace from 3.0.X to 3.11.2 Cluster which already have keyspaces
Date Mon, 02 Dec 2019 15:27:43 GMT
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 - <slmnjobs@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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