What is Greenplum: Greenplum Database is a massively parallel processing (MPP) database server based on PostgreSQL open-source technology. MPP (also known as a shared nothing architecture) refers to systems with two or more processors which cooperate to carry out an operation - each processor with its own memory, operating system and disks.
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To understand Greenplum: http://patodirahul.blogspot.com/2011/04/understanding-greenplum.html
To Install: http://patodirahul.blogspot.com/2011/04/installing-greenplum-sne-ce.html