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From Richard Low <rich...@wentnet.com>
Subject Re: cassandra 1.2.5- virtual nodes (num_token) pros/cons?
Date Tue, 06 Aug 2013 08:49:13 GMT
On 6 August 2013 08:40, Aaron Morton <aaron@thelastpickle.com> wrote:

> The reason for me looking at virtual nodes is because of terrible
> experiences we had with 0.8 repairs and as per documentation (an logically)
> the virtual nodes seems like it will help repairs being smoother. Is this
> true?
>
> I've not thought too much about how they help repair run smoother, what
> was the documentation you read ?
>

There might be a slight improvement but I haven't observed any.  The
difference might be that, because every node shares replicas with every
other (with high probability), a single repair operation does the same work
on the node it was called on, but the rest is spread out over the cluster,
rather than just the RF nodes either side of the repairing node.  This
means the post-repair compaction work will take less time and the length of
time a node is loaded for during repair is less.

However, the other benefits of vnodes are likely to be much more useful.

Richard.

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