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From Vlad <qa23d-...@yahoo.com>
Subject Re: system_auth replication strategy
Date Sun, 02 Apr 2017 18:21:32 GMT
Actually if factor is equal to total number of nodes with SimpleStrategy one copy will be placed
on each node.Does LOCAL_ONE know to choose local (the same) node with SimpleStrategy? 

    On Sunday, April 2, 2017 4:02 PM, Sam Tunnicliffe <sam@beobal.com> wrote:
 

 
auth logins for super users is 101 replicas serving the read

This only applies to the default superuser (i.e. 'cassandra'), which is one of the reasons
for recommending it is only used during initial setup[1]. Reads for all other users, including
superusers, are done at LOCAL_ONE
[1] http://cassandra.apache.org/doc/latest/operating/security.html#authentication
On Sun, Apr 2, 2017 at 7:07 AM, Jeff Jirsa <jjirsa@apache.org> wrote:

> You should use a network topology strategy with high RF in each DC


There's some debate here - some blogs/speakers will say to put a replica on each instance,
but that falls down above a few dozen instances. Imagine if you have (for example) 200 instances
per DC, auth logins for super users is 101 replicas serving the read - that's a really slow
login that's likely to fail (think about thread pools on the coordinator doing the read response
handling, it's an ugly ugly mess).

Normal logins do use LOCAL_ONE though so if there are lots of replicas, auth will be faster
- so use 5-10 replicas per DC, and crank up the caching timeouts as well





   
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