The main reason for mentioning the disk I/O demand was that all the other (classic) Unixes only include CPU demand as part of system load and not I/O. This will

The main reason for mentioning the disk I/O demand was that all the other (classic) Unixes only include CPU demand as part of system load and not I/O. This will confuse sysadmins coming from Solaris/HP-UX/AIX/BSD background. The other reason is that I've troubleshooted plenty of Linux load spike problems that are about CPU demand spikes only, usually due to some spinlock that gets held unusually long or some interrupt storm issue or some sort of a "database logon storm" due to connection pools in the app server suddenly creating thousands of additional DB connections...