+1 for more documentation (I guess contributions are always welcomed).... I will try to write it down sometime when we have a bit more time...
0.8 nodetool ring command adds the DC and RAC information.... http://www.datastax.com/dev/blog/deploying-cassandra-across-multiple-data-centers http://www.datastax.com/products/opscenter Hope this helps... Regards, </VJ> On Wed, Jun 15, 2011 at 7:24 PM, AJ <a...@dude.podzone.net> wrote: > Ok. I understand the reasoning you laid out. But, I think it should be > documented more thoroughly. I was trying to get an idea as to how flexible > Cass lets you be with the various combinations of strategies, snitches, > token ranges, etc.. > > It would be instructional to see what a graphical representation of a > cluster ring with multiple data centers looks like. Google turned-up > nothing. I imagine it's a multilayer ring; one layer per data center with > the nodes of one layer slightly offset from the ones in the other (based on > the example in the wiki). I would also like to know which node is next in > the ring such so as to understand replica placement in, for example, the > OldNetworkTopologyStrategy when it's doc states, > > "...It places one replica in a different data center from the first (if > there is any such data center), the third replica in a different rack in the > first datacenter, and any remaining replicas on the first unused nodes on > the ring." > > I can only assume for now that "the ring" referred to is the "local" ring > of the first data center. > > > > On 6/15/2011 5:51 PM, Vijay wrote: > > No it wont.... it will assume you are doing the right thing... > > Regards, > </VJ> > > > > On Wed, Jun 15, 2011 at 2:34 PM, AJ <a...@dude.podzone.net> wrote: > >> Vijay, thank you for your thoughtful reply. Will Cass complain if I >> don't setup my tokens like in the examples? >> >> >> On 6/15/2011 2:41 PM, Vijay wrote: >> >> All you heard is right... >> You are not overriding Cassandra's token assignment by saying here is your >> token... >> >> Logic is: >> Calculate a token for the given key... >> find the node in each region independently (If you use NTS and if you set >> the strategy options which says you want to replicate to the other >> region)... >> Search for the ranges in each region independntly >> Replicate the data to that node. >> >> For multi DC cassandra needs nodes to be equally partitioned within each >> dc (If you care that the load equally distributed).... as well as >> there shouldn't be any collusion of tokens within a cluster.... >> >> The documentation tried to explain the same and the example in the >> documentation. >> Hope this clarifies... >> >> More examples if it helps.... >> >> DC1 Node 1 : token 0 >> DC1 Node 2 : token 8.. >> >> DC2 Node 1 : token 4.. >> DC2 Node 1 : token 12.. >> >> or >> >> DC1 Node 1 : token 0 >> DC1 Node 2 : token 1.. >> >> DC2 Node 1 : token 8.. >> DC2 Node 1 : token 7.. >> >> Regards, >> </VJ> >> >> >> >> On Wed, Jun 15, 2011 at 12:28 PM, AJ <a...@dude.podzone.net> wrote: >> >>> On 6/15/2011 12:14 PM, Vijay wrote: >>> >>> Correction.... >>> >>> "The problem in the above approach is you have 2 nodes between 12 to 4 >>> in DC1 but from 4 to 12 you just have 1" >>> >>> should be >>> >>> "The problem in the above approach is you have 1 node between 0-4 (25%) >>> and and one node covering the rest which is 4-16, 0-0 (75%)" >>> >>> Regards, >>> </VJ> >>> >>> >>> Ok, I think you are saying that the computed token range intervals are >>> incorrect and that they would be: >>> >>> DC1 >>> *node 1 = 0 Range: (4, 16], (0, 0] >>> >>> node 2 = 4 Range: (0, 4] >>> >>> DC2 >>> *node 3 = 8 Range: (12, 16], (0, 8] >>> >>> node 4 = 12 Range: (8, 12] >>> >>> If so, then yes, this is what I am seeking to confirm since I haven't >>> found any documentation stating this directly and that reference that I gave >>> only implies this; that is, that the token ranges are calculated per data >>> center rather than per cluster. I just need someone to confirm that 100% >>> because it doesn't sound right to me based on everything else I've read. >>> >>> SO, the question is: Does Cass calculate the consecutive node token >>> ranges A.) per cluster, or B.) for the whole data center? >>> >>> From all I understand, the answer is B. But, that documentation >>> (reprinted below) implies A... or something that doesn't make sense to me >>> because of the token placement in the example: >>> >>> "With NetworkTopologyStrategy, you should calculate the tokens the nodes >>> in each DC independantly... >>> >>> DC1 >>> node 1 = 0 >>> node 2 = 85070591730234615865843651857942052864 >>> >>> DC2 >>> node 3 = 1 >>> node 4 = 850705917302346158658436518579 >>> 42052865" >>> >>> >>> However, I do see why this would be helpful, but first I'm just asking if >>> this token assignment is absolutely mandatory >>> or if it's just a technique to achieve some end. >>> >>> >>> >>> >> >> > >
