[techscruggs]

Its a bad solution for OLTP. C-stores are read optimized while a typical (row-oriented) rdbms is write optimized. Read optimized storage is typically accomplished via a write buffer that is flushed to a read store at a certain epoch.

Basically, if you need to be able to immediately read the data you just wrote, a cstore is a bad choice.

[ironchef]

There's also in betweens. Cassandra for example is a bit of a hybrid. It writes quite well even though it has some columnar / big-table aspects.