In a recent Oracle Exadata FAQ, Kevin Closson writes:
Q. [...] don’t some of the DW vendors split the data up in a shared nothing method. Thus when the data has to be repartitioned it gets expensive. Whereas here you just add another cell and ASM goes to work in the background. (depending upon the ASM power level you set.)
A. All the DW Appliance vendors implement shared-nothing so, yes, the data is chopped up into physical partitions. If you add hardware to increase performance of queries against your current dataset the data will have to be reloaded into the new partitioning scheme. As has always been the case with ASM, adding new disks-and therefore Exadata Storage Server cells-will cause the existing data to be redistributed automatically over all (including the new) drives. This ASM data redistribution is an online function.
Hmm. That sounds much like the story I’ve heard from various other data warehousing DBMS vendors as well.
Rather than try to speak for them, however, I’ll just post this and see whether they choose to add anything to the comment thread.