posted 10 years ago
Hadoop using MapReduce is a batch processing framework. Typically you churn through a lot of data in queries that take seconds, minutes or longer.
Hbase and Accumulo offer something more like a database modelled on the Google BigTable paper. These can service low-latency end-user facing queries. Accumulo has a number of particular extensions over HBase, in particular around much finer grained security labelling and the ability to efficiently run server-side functions.
Garry