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Re: system_auth keyspace replication factor


I suspect some of the intermediate queries (determining role, etc) happen at quorum in 2.2+, but I don’t have time to go read the code and prove it. 

This isn’t true. Aside from when using the default superuser, only CRM::getAllRoles reads at QUORUM (because the resultset would include the default superuser if present). This is only called during execution of a LIST ROLES statement and isn’t on the login path.

From the driver log you can see that the actual authentication exchange happens quickly, so I’d say that the problem described in CSHARP-436 is a more likely candidate. 

Sadly, this recommendation is out of date / incorrect.  For `system_auth` we are mostly using a formula like `RF=min(num_dc_nodes, 5)` and see no issues.

+1 to that, RF=N is way over the top. 

Thanks,
Sam


On 26 Nov 2018, at 09:44, Oleksandr Shulgin <oleksandr.shulgin@xxxxxxxxxx> wrote:

On Fri, Nov 23, 2018 at 5:38 PM Vitali Dyachuk <vdjatsuk@xxxxxxxxx> wrote:

We have recently met a problem when we added 60 nodes in 1 region to the cluster
and set an RF=60 for the system_auth ks, following this documentation https://docs.datastax.com/en/cql/3.3/cql/cql_using/useUpdateKeyspaceRF.html

Sadly, this recommendation is out of date / incorrect.  For `system_auth` we are mostly using a formula like `RF=min(num_dc_nodes, 5)` and see no issues.

Is there a chance to correct the documentation @datastax?

Regards,
--
Alex