Today's SQL Server tip

MONITOR DISK USAGE v7.0
In a perfect database world, there would be no disk drives to store 
data, only online memory. In the real world, we need to be cognizant of 
our disk drives and disk arrays. You can do this with Windows NT's 
Performance Monitor in conjunction with SQL Server's Performance 
Counters.

The first step is to turn on the disk performance counters, which can 
be accomplished at an operating system command prompt. By issuing the 
command C:>diskperf -y and then rebooting your server, you turn on the 
underlying counters for monitoring hard drive activity. This exposes 
the disk information to the NT Performance Monitor for evaluation.

A cautionary note: Do not keep these counters turned on. Use them only 
when you are trying to ascertain information about your disk drive 
subsystem(s). Performance counters are for troubleshooting/analysis 
only. You can turn them off by issuing the command C:>diskperf -n and 
rebooting the server.

By performing the above steps, you can now analyze your disk subsystems 
by starting NT Performance Monitor and selecting one of the many 
individual counters from the "PhysicalDisk:" category for your 
particular server.

You can read in depth about disk and performance counters in MSDN Books 
Online.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/startsql/getstart_4fht.asp