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The "ArchitectureOverview" page has been changed by tuxracer69. http://wiki.apache.org/cassandra/ArchitectureOverview?action=diff&rev1=4&rev2=5 -------------------------------------------------- Information is mainly based on [[http://assets.en.oreilly.com/1/event/27/Cassandra_%20Open%20Source%20Bigtable%20+%20Dynamo%20Presentation.pdf|J Ellis OSCON 09 presentation ]] - == Motivation == - Scaling reads to a relational database is hard Scaling writes to a relational database is virtually impossible - - ... and when you do, it usually isn't relational anymore Why Cassandra * MySQL drives too many random I/Os @@ -83, +79 @@ - + == Keys distribution and Partition == Dynamo architecture & Lookup + + + In a ring of nodes A, B, C, D, E, F and G + Nodes B, C and D store keys in the range (''a'',''b'') including key ''k'' + + + You can decide where the key should go in Cassandra using the {{{IntitialToken}}} parameter for your {{{Partitioner}}}, see [[StorageConfiguration|Storage Configuration]] Architecture details @@ -200, +203 @@ write replica count > replication factor). - + You get consistency if R + W > N, where R is the number of records to read, W is the number of records to write, and N is the replication factor. A ConsistencyLevel of ONE means R or W is 1. A ConsistencyLevel of QUORUM means R or W is ceiling((N+1)/2). A ConsistencyLevel of ALL means R or W is N. So if you want to write with a ConsistencyLevel of ONE and then get the same data when you read, you need to read with ConsistencyLevel ALL. Cassandra vs MySQL with 50GB of data
