NRW Notation

Describes how Distributed Databases deal with consistency and reads and writes.

  • R: Number of nodes that are read from
  • W: Number of nodes that are written to
  • N: Total number of nodes in the cluster
NRW ConfigurationResult
W=N R=1Read performance optimized, write costly (strong consistency)
W=1 R=NWrite performance optimized, read costly (strong consistency)
W+R <= NEventual consistency
W+R > NQuorum assembly, every read will see at least one copy of currently most recent update
N > W > 1Most common setting for NoSql Databases