For Exadata documentation, please refer to my blog http://blog.vishalgupta.com/2011/10/15/oracle-exadata-documentation/. It gives in detail how to get the Oracle exadata documentation. Please ensure that you have the Exadata license before following the steps in the blog. Unfortunately Oracle does not publicly publish the exadata documentation, and is only available for existing exadata customers.
For white paper and other data sheets please refer to this link on oracle website. http://www.oracle.com/us/products/database/exadata-database-machine/overview/index.html
You might have added: "... and each has its own weaknesses."
One of the most obvious being the incredible cost of porting application code to them. I recently looked into moving an application from Oracle to Teradata ... the cost of the software changes (including design, coding, and end-to-end testing) was 300% greater than the cost of the hardware.
If you are thinking about a very low cost solution, you could stick with Oracle, and try timesTen (If it is OLAP or small database)
Or even try Oracle 11g with FLASH.
Can you tell use what is the version of your database, and what is the issue that you are dealing with?
If your version is 10g or bellow, Oracle 11g might improve a lot of performance with it´s new resources for instance reference partition (it may allow you to partition sub tables that didn´t had a match before).
Also in reply to the original poster you can look into the oracle database appliance which is like a two node RAC in a box... http://www.oracle.com/us/products/database/database-appliance/overview/index.html