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Date: Fri, 21 Jul 2017 01:36:01 +0000 (UTC)
From: "Jeremy Hanna (JIRA)" <jira@apache.org>
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Subject: [jira] [Comment Edited] (CASSANDRA-13701) Lower default num_tokens
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archived-at: Fri, 21 Jul 2017 01:36:08 -0000


    [ https://issues.apache.org/jira/browse/CASSANDRA-13701?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16095638#comment-16095638 ] 

Jeremy Hanna edited comment on CASSANDRA-13701 at 7/21/17 1:35 AM:
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Adding datacenters with the new algorithm requires some additional configuration.  We would need to make users aware of that trade-off when using that algorithm and the benefits of fewer token ranges per node.  It's talked about [here|http://docs.datastax.com/en/dse/5.1/dse-dev/datastax_enterprise/config/configVnodes.html] but we should make it clearer in the apache docs as well.  We can point to those in the comments around vnode tokens.

So it would be nice to add some more information [here|http://cassandra.apache.org/doc/latest/configuration/cassandra_config_file.html#allocate-tokens-for-keyspace] and then perhaps in [here|http://cassandra.apache.org/doc/latest/operating/topo_changes.html] with an additional section about adding a datacenter.

And Jeff: good point about the token allocation - would be good to track that down before making the new algorithm the default.  However even still I think even with the old algorithm we could at the very least halve the number of default vnode ranges.


was (Author: jeromatron):
Adding datacenters with the new algorithm requires some additional configuration.  We would need to make users aware of that trade-off when using that algorithm and the benefits of fewer token ranges per node.  It's talked about [here|http://docs.datastax.com/en/dse/5.1/dse-dev/datastax_enterprise/config/configVnodes.html] but we should make it clearer in the apache docs as well.  We can point to those in the comments around vnode tokens.

So it would be nice to add some more information [here|http://cassandra.apache.org/doc/latest/configuration/cassandra_config_file.html#allocate-tokens-for-keyspace] and then perhaps in [here|http://cassandra.apache.org/doc/latest/operating/topo_changes.html] with an additional section about adding a datacenter.

> Lower default num_tokens
> ------------------------
>
>                 Key: CASSANDRA-13701
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13701
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Chris Lohfink
>            Assignee: Chris Lohfink
>            Priority: Minor
>
> For reasons highlighted in CASSANDRA-7032, the high number of vnodes is not necessary. It is very expensive for operations processes and scanning. Its come up a lot and its pretty standard and known now to always reduce the num_tokens within the community. We should just lower the defaults.


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