On Sat, Apr 3, 2010 at 8:23 PM, Mike Gallamore <mike.e.gallam...@googlemail.com> wrote: >> > I didn't mean a real time determination, more of if the nodes aren't > identical. For example if you have a cluster made up of a bunch of EC2 light > instances and decide to add a large instance, it would be nice if the new > node would get a proportional amount of work based on what its system specs > are.
Sure, set the token(s) appropriately. >> >>> perhaps a preferred hash range not just a token (and presumably everything >>> else would automatically rebalance itself to make that happen) >>> >> >> Unclear what this would do. > Well rather than getting half of the most busy nodes work (which is how I > understand it works now) you'd get an amount of work that is proportional to > the power of the node. Assuming you allow it to automatically assign its own token, the new node will get have the range of the node with the most data, not the most 'busy'. The amount of work being done by the nodes is not a consideration, nor would you want automatic selection of that within cassandra except with significant support for long term trend collection and analysis, pluggable policies for calculating 'load', etc. >> >> Or just set the token specifically for each node you bootstrap. >> Starting a node and crossing your fingers on its token selection is a >> recipe for interesting times :) > Can you specify a token based on a real key value? How do you know what token > to use to make sure that locally relevant data gets at least one copy stored > locally? Again, placement strategy is what you want to investigate. > My understanding is rackawarestrategy puts the data on the next node in the > token ring that is in a different datacenter. The problem is if you want a > specific "other datacenter" not just the next one in the list. Right, I suggested looking at the source as an example. If you want a more sophisticated placement policy, write one. They are not complicated and you will have a much deeper understanding of the mechanism. IMO, pluggable placement is a remarkable feature. b
