[eksith]

We don't run a shopping cart, but one of our databases at present is at 11.3TB on PostgreSQL 9.1 and we're by no means dealing with small sets. We routinely juggle several Gigs at a time when we need to do analytics. We didn't see a reason to put this on a cloud since bandwidth + electricity is still cheaper for us than bandwidth + storage in the cloud at present.

[monstrado]

If you have a few servers to spare, I'd recommend installing Cloudera Impala on them. You can use Apache Sqoop to pull the data out of Postgres and into HDFS.. Directly after, you can run SQL queries which will query the data in parallel (similar to redshift).