Nearly all Linux and Unix systems have an iostat report; Solaris may offer the sar -d report. If you are using a filer, for example from NetApp, by issuing a remote shell sysstat command directly to the filer, you can gather IO statistics similar to those reported by iostat. If you're a DBA, you may not have permission to do this, so you will need to rely on the wait interface and operating system tracing to build a strong IO subsystem case.

I will focus on the iostat report because it provides more detail than the sar -d report and filer sysstat IO reports. Plus, if you understand the iostat report, you can easily understand the others.

Figure 4-22 is a typical iostat report for a very small IO subsystem. It is common for a thousand lines to be returned. When studying the IO subsystem, it can be a good idea to load the iostat data into Oracle and filter on the response time (await, svctm) and utilization (%util) columns to find offensive IO patterns.