nodetool ring is, IMHO, quite confusing in the case of multiple datacenters.
Might be easier to think of it as two rings:
in your DC1 ring you have two nodes, and since the tokens are balanced,
assuming your rows are randomly distributed you'll have half the data on each,
since your replication factor in DC is 1.
In your DC2 'ring' you have one node, and with a replication factor of 1 in
DC2, all data will go on that node.
So you would expect to have n MB of data on XXX.YYY and XXX.ZZZ and 2n MB of
data on AAA and BBB, and that's what you have, to a T. :)
In other words, the fact that you injecte node AAA.BBB with a token that seems
to divide the ring into uneven portions, because the DC1 ring is only DC1, it's
not left unbalanced by the new node. If you added a second node to DC2 you
would want to give it a token of something like
106338239662793269832304564822427565952 so that the DC2 is also evenly balanced.
--DRS
On Feb 9, 2012, at 11:00 PM, Ravikumar Govindarajan wrote:
> Hi,
>
> I was trying to setup a backup DC from existing DC.
>
> State of existing DC with SimpleStrategy & rep_factor=1.
>
> ./nodetool -h localhost ring
> Address DC Rack Status State Load Owns
> Token
>
>
> 85070591730234615865843651857942052864
> XXX.YYY DC1 RAC1 Up Normal 187.69 MB 50.00%
> 0
> XXX.ZZZ DC1 RAC1 Up Normal 187.77 MB 50.00%
> 85070591730234615865843651857942052864
>
> After adding backup DC with NetworkTopologyStrategy {DC1:1,DC2:1}, the output
> is as follows
>
> ./nodetool -h localhost ring
> Address DC Rack Status State Load Owns
> Token
>
> 85070591730234615865843651857942052864
> XXX.YYY DC1 RAC1 Up Normal 187.69 MB 50.00% 0
>
> AAA.BBB DC2 RAC1 Up Normal 374.59 MB 11.99%
> 20392907958956928593056220689159358496
> XXX.ZZZ DC1 RAC1 Up Normal 187.77 MB 38.01%
> 85070591730234615865843651857942052864
>
> As per our app rules, all writes will first go through DC1 and then find it's
> way to DC2. Since the "Owns" percentage has drastically changed, will it mean
> that the DC1 nodes will become unbalanced for future writes?
>
> We have a very balanced ring in our production with all nodes serving almost
> equal volume data as of now in DC1. Will setting up a backup DC2 disturb the
> balance?
>
> Thanks and Regards,
> Ravi
