It's not a secret that majority of popular relational DBMSes (e.g. Oracle, MS SQL Server or MySQL) were originally designed for transactional processing. Besides other features, they employ row-based data storage and SMP-architecture which is good for OLTP systems, but in case of analytical applications (like enterprise data warehouses) that require heavy scans and data aggregation, this is far not the best case. Usually, analytical workloads are handled much better by purpose-built analytical DBMSes. If you want to try such DBMS without hassle of dealing with sales people there're at least 4 options to try an analytical database yourself and for free:
Greenplum Community Edition
This is analytical relational DBMS designed for heavy workloads on terabytes of data. Its core is derived from PosgreSQL, which assumes that data is still stored in rows, however Greenplum has MPP architecture.
The free community edition is limited to 2 CPU sockets or 8 virtual cores.
Infobright Community Edition
Infobright is truly columnar DBMS, however not so popular as Sybase IQ or Vertica. The free Community Edition is simplified version of commercial Enterprise edition and is open-sourced. It lacks some features that can be important for large-scale deployment: DML, Temporary Tables, Parallel Query Execution and some other. Nevertheless, even this limited edition can show 5x-10x performance improvement on small datasets (say, up to 0.5TB).
LucidDB is also columnar DBMS which is open-source from origin. I've not heard about any large-scale deployments of LucidDB, however some benchmarks show impressive improvement over MySQL. So, if you use the latter for analytical workloads give a closer look at LucidDB.
Another one open-source columnar DBMS which was designed in the Netherlands. Features include enhanced support for XML and multimedia objects, and support for modern CPU architecture.