Aaron - I read about the virtual nodes at http://www.datastax.com/dev/blog/virtual-nodes-in-cassandra-1-2

On Tue, Aug 6, 2013 at 4:49 AM, Richard Low <richard@wentnet.com> wrote:
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.