
168 DS8800 Performance Monitoring and Tuning
Physical I/O profile
The physical I/O profile is based on the logical I/O with the assumption that the database
provides cache hits to 90% of the read I/Os. All write I/Os are assumed to require a
physical I/O. This physical I/O profile results in a read miss ratio of (1 - 0.9) = .1 or 10%.
Table 5-6 is an example, and every application has different characteristics.
Table 5-6 Physical I/O profile
As you can see in Table 5-6, to meet the peak workloads, you need to design an I/O
subsystem to support 6000 random reads/sec and 6000 random writes/sec:
Physical I/Os The number of physical I/Os per second ...