Tuning example: CPU and I/O saturation

One experiment on a CPU-bound query found near-linear scaling in performance by adding CPUs until the I/O subsystem became saturated. At that point, additional CPU resources did not improve performance. The query performs a table scan on an 800MB table with 30 partitions, using 16K I/O. Table 24-3 shows the CPU scaling.

**Table 24-3: Scaling of engines and worker processes**
Engines	Elapsed time, (in seconds)	CPU utilization	I/O saturation	Throughput per device, per second
1	207	100%	Not saturated	.13MB
2	100	98.7%	Not saturated	.27MB
4	50	98%	Not saturated	.53MB
8	27	93%	100% saturated	.99MB