Fabulous answer on StackExchange to a question that is in the mind of the users of relational databases that have heard of NoSQL.
Distributed database systems are complex critters and come in a
number of different flavours. If I dig deep in to the depths of my
dimly remembered distributed systems papers I did at university
(roughly 15 years ago) I’ll try to explain some of the key
engineering problems to building a distributed database system.
Original title and link: Why Can’t RDBM Cluster the Way NoSQL Does? Distributed Database Architecture 101 ( ©myNoSQL)