Guidance on Migrating from SimpleSnitch and SimpleStrategy in Cassandra 3.11 Cluster

[Nick Jonas <jo...@gmail.com>]

Hi Community,

We currently have a 3-node Cassandra 3.11 production cluster that was
initially set up with the following configuration:

   -

   *Snitch:* endpoint_snitch: SimpleSnitch
   -

   *Keyspace replication:* {'class': 'SimpleStrategy',
   'replication_factor': '3'}

Unfortunately, this setup was not ideal for a production environment, and
we're now looking to correct it. Specifically, we want to:

   1.

   *Switch to a more appropriate snitch* (e.g., GossipingPropertyFileSnitch)
   2.

   *Update keyspaces to use* NetworkTopologyStrategy

I would appreciate any advice on the best practices for making these
changes in a running production cluster. My main concerns are:

   -

   What is the safest order of operations?
   -

   Will switching the snitch or replication strategy cause any *data loss
   or availability issues*?
   -

   Do we need to perform any additional steps (e.g., full repair, rolling
   restart, etc.)?
   -

   Are there specific * known issues* when migrating from SimpleSnitch +
   SimpleStrategy to a production-grade setup?

Thanks in advance for your guidance!

Re: Guidance on Migrating from SimpleSnitch and SimpleStrategy in Cassandra 3.11 Cluster

[manish khandelwal <ma...@gmail.com>]

Hi Nick

1. Take Backup.
2. Migrate the snitch. Refer
https://docs.datastax.com/en/cassandra-oss/3.x/cassandra/operations/opsSwitchSnitch.html
and
https://dba.stackexchange.com/questions/314862/how-do-i-change-the-cassandra-topology-snitch-in-a-multi-az-cluster
3. For altering the keyspace, run alter keyspace command as
 ALTER KEYSPACE keyspace_name WITH REPLICATION = {'class':
'NetworkTopologyStrategy', '<datacentername>': 3};
4. Run repair if I am not mistaken should not be required for single DC.
Refer
https://docs.datastax.com/en/cassandra-oss/3.0/cassandra/operations/opsChangeKSStrategy.html
5. Test on a test environment first before applying on production.

Regards
Manish


On Thu, Jul 17, 2025 at 1:03 PM Nick Jonas <jo...@gmail.com>
wrote:

> Hi Community,
>
> We currently have a 3-node Cassandra 3.11 production cluster that was
> initially set up with the following configuration:
>
>    -
>
>    *Snitch:* endpoint_snitch: SimpleSnitch
>    -
>
>    *Keyspace replication:* {'class': 'SimpleStrategy',
>    'replication_factor': '3'}
>
> Unfortunately, this setup was not ideal for a production environment, and
> we're now looking to correct it. Specifically, we want to:
>
>    1.
>
>    *Switch to a more appropriate snitch* (e.g.,
>    GossipingPropertyFileSnitch)
>    2.
>
>    *Update keyspaces to use* NetworkTopologyStrategy
>
> I would appreciate any advice on the best practices for making these
> changes in a running production cluster. My main concerns are:
>
>    -
>
>    What is the safest order of operations?
>    -
>
>    Will switching the snitch or replication strategy cause any *data loss
>    or availability issues*?
>    -
>
>    Do we need to perform any additional steps (e.g., full repair, rolling
>    restart, etc.)?
>    -
>
>    Are there specific * known issues* when migrating from SimpleSnitch +
>    SimpleStrategy to a production-grade setup?
>
> Thanks in advance for your guidance!
>