All depends on the workload, aggregates are more often CPU capped than IO cap in workloads we use in-house. We have a PostgreSQL server with 16GB of memory (the

All depends on the workload, aggregates are more often CPU capped than IO cap in workloads we use in-house. We have a PostgreSQL server with 16GB of memory (the database total is over 80GB, but the table that is hit the most is under 3GB, the rest is just BLOB's) - more than enough to keep the relevant data in memory. Most of the time running some aggregate queries that hit the database server pretty hard are spent in USER, not IOWAIT. It's pretty annoying, because I frequently see my CPU usage at 50% (one of two cores maxed) when I know these queries could be parallelized and take advantage of the second core (or more).