Hi Daniel, Clients do not specify the partition when making a request. A client can request any key from any node in the cluster and Riak will return the associated value.
Thanks, Dan Daniel Reverri Developer Advocate Basho Technologies, Inc. d...@basho.com On Thu, Dec 16, 2010 at 6:01 PM, Daniel Woo <daniel.y....@gmail.com> wrote: > Hi Mark, > > Thanks for your explanation, so in this case the partitions would be > re-distributed > > *from* > > Node1: p1 ~ p16 > Node2: p17 ~ p32 > Node3: p33 ~ p48 > Node4: p49 ~ p64 > > *to * > Node1: p1 ~ p13 (remove 3 partitions) > Node2: p17 ~ p29 (remove 3 partitions) > Node3: p33 ~ p45 (remove 3 partitions) > Node4: p49 ~ p61 (remove 3 partitions) > Node5: p14, 15, 16, 30, 31, 32, 46, 47, 48, 62, 63, 64 (aprox 1/5 > partitions will be transferred to this new node) > > Since there is no centralized node in Riak, how do we know the partition 32 > is moved to node 5 from the client caller? Cassandra seems break half of the > adjacent node's data into the new node, that will be easy for the client to > search for the datum just around the node-circle clockwise, although it > causes unbalanced data distribution and you have to move them by command > lines. Riak seems to have this solved by moving partitions into new nodes > equally, that's very interesting, how do you guys make it? If the client > caller queries for partition 32 which was originally on node 2, how do the > client know it's on a new node now? > > Thanks, > Daniel > > > On Fri, Dec 17, 2010 at 6:56 AM, Mark Phillips <m...@basho.com> wrote: > >> Hey Daniel, >> >> [snip] >> >> > So, I guess Riak would have to re-hash the whole partitions into all the >> 5 >> > nodes, right? Is this done lazily when the node finds the requested data >> is >> > missing? >> > Or is there a way to handle this with consistent re-hashing so we can >> avoid >> > moving data around when new nodes added? >> > >> >> Riak won't rehash all the partitions in the ring when new nodes are >> added. When you go from 4 -> 5 nodes, for example, approx. 1/5 of the >> existing partitions are transferred to the new node. The other 4/5s of >> the partitions will remain unchanged. As far as moving data around >> when new nodes are added, this is impossible to avoid. Data needs to >> be handed off to be spread around the ring. >> >> Hope that helps. >> >> Mark >> > > > > -- > Thanks & Regards, > Daniel > > _______________________________________________ > riak-users mailing list > riak-users@lists.basho.com > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com > >
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