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The "Operations" page has been changed by JonathanEllis. http://wiki.apache.org/cassandra/Operations?action=diff&rev1=87&rev2=88 -------------------------------------------------- * The corollary to this is, if you want to start with a single DC and add another later, when you add the second DC you should add as many nodes as you have in the first rather than adding a node or two at a time gradually. - Replication factor is not really intended to be changed in a live cluster either, but increasing it may be done if you (a) read at ConsistencyLevel.QUORUM or ALL (depending on your existing replication factor) to make sure that a replica that actually has the data is consulted, (b) are willing to accept downtime while anti-entropy repair runs (see below), or (c) are willing to live with some clients potentially being told no data exists if they read from the new replica location(s) until repair is done. + Replication factor is not really intended to be changed in a live cluster either, but increasing it is conceptually simple: update the replication_factor from the CLI (see below), then run repair against each node in your cluster so that all the new replicas that are supposed to have the data, actually do. + + Until repair is finished, you have 3 options: + * read at ConsistencyLevel.QUORUM or ALL (depending on your existing replication factor) to make sure that a replica that actually has the data is consulted + * continue reading at lower CL, accepting that some requests will fail (usually only the first for a given query, if ReadRepair is enabled) + * take downtime while repair runs The same options apply to changing replication strategy.
