On Tue, Jun 5, 2012 at 4:30 PM, Jim Ancona <jim@anconafamily.com> wrote:
It might be a good idea for the documentation to reflect the tradeoffs more clearly.

Here's a proposed addition to the Secondary Index FAQ at http://wiki.apache.org/cassandra/SecondaryIndexes

Q: How does choice of Consistency Level affect cluster availability when using secondary indexes?
A: Because secondary indexes are distributed, you must have CL level nodes available for all token ranges in the cluster in order to complete a query. For example, with RF = 3, when two out of three consecutive nodes in the ring are unavailable, all secondary index queries at CL = QUORUM will fail, however secondary index queries at CL = ONE will succeed. This is true regardless of cluster size.