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From "Brandon Williams (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4119) Support multiple non-consecutive tokens per host (virtual nodes)
Date Fri, 01 Jun 2012 17:40:23 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287556#comment-13287556
] 

Brandon Williams commented on CASSANDRA-4119:
---------------------------------------------

I smoke tested your git branch and saw write performance was about 33% slower than trunk.
 I haven't dug into why that is yet though.
                
> Support multiple non-consecutive tokens per host (virtual nodes)
> ----------------------------------------------------------------
>
>                 Key: CASSANDRA-4119
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4119
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Sam Overton
>            Assignee: Sam Overton
>              Labels: virtualnodes, vnodes
>
> This is the parent ticket for the virtual nodes implementation which was proposed here:
http://www.mail-archive.com/dev@cassandra.apache.org/msg03837.html and discussed in the subsequent
thread.
> The goals of this ticket are:
> * reduced operations complexity for scaling up/down
> * reduced rebuild time in event of failure
> * evenly distributed load impact in the event of failure
> * evenly distributed impact of streaming operations
> * more viable support for heterogeneity of hardware
> The intention is that this can be done in a way which is
> * fully backwards-compatible
> * optionally enabled
> The latter of these can be trivially achieved by setting the number of tokens per host
to 1, to reproduce the existing behaviour.
> Implementation detail can be added and discussed in the sub-tickets, but here is an overview
of the proposed changes:
> * TokenMetadata will allow multiple tokens per host
> * Hosts will be referred to by a UUID instead of token (e.g. in Gossip, when storing
hints, etc.)
> * A bootstrapping node can get multiple tokens from initial_token (comma separated) or
by random allocation
> * NetworkTopologyStrategy will be extended to be aware of virtual nodes so that replicas
are not placed on the same host (similar to racks now)
> * Repairs will be staggered similar to CASSANDRA-3721
> * Nodetool operations will be virtual-node aware, while maintaining backwards compatibility
(ie. existing scripts won't have to change)
> * Upgrade will be a standard rolling upgrade, with optional rolling migration to full
vnode support

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