the reason for the default of 256 vnodes is because at that many tokens the
random distribution of tokens is enough to balance out each nodes token
allocation almost evenly. any less and some nodes will get far more
unbalanced, as Avi has shown. In 3.0 there is a new token allocating
algorithm however it requires configuring prior to adding a node and also
only really works well if your RF=# of racks, or you only use 1 rack. have
a look around for the allocate_token_keyspace option for more details.
