(8) NRW Analysis.
NRW (Node, Read, Write) analysis is used to analyze the
characteristics of distributed database how they will trade off
Consistency, Read and Write performance [24].
Here,
N is the number of Nodes keeping copies of distributed record;
W, number of nodes that must successfully acknowledge for a
Write to be successfully committed.
R, the number of nodes that must send back the data to be
accepted as read by the system.
The majority of NoSQL databases uses N > W > 1 i.e. more
than one write must complete, but not all nodes need to be updated
immediately.
Tables 4 and 5 categorize the NoSQL according to NRW [25,24].
The ‘‘Read Repair’’ algorithm is often implemented to improve
consistency when R = 1.
The following are some more muscle with various Consistency
levels [24].