How to measure disk-performance under Windows?

There is a built-in disk performance checker in Windows called winsat:

winsat disk -drive g

(Run winsat with Administrator privileges)

More info: Info on winsat disk on technet.microsoft.com/en-us/library/cc742157.aspx

e.g:

C:\WINDOWS\system32>winsat disk -drive g
Windows System Assessment Tool
> Running: Feature Enumeration ''
> Run Time 00:00:00.00
> Running: Storage Assessment '-drive g -ran -read'
> Run Time 00:00:04.17
> Running: Storage Assessment '-drive g -seq -read'
> Run Time 00:00:08.64
> Running: Storage Assessment '-drive g -seq -write'
> Run Time 00:00:17.47
> Running: Storage Assessment '-drive g -flush -seq'
> Run Time 00:00:03.53
> Running: Storage Assessment '-drive g -flush -ran'
> Run Time 00:00:04.16
> Disk  Random 16.0 Read                       21.05 MB/s          6.0
> Disk  Sequential 64.0 Read                   38.29 MB/s          4.9
> Disk  Sequential 64.0 Write                  39.67 MB/s          4.9
> Average Read Time with Sequential Writes     1.324 ms          7.4
> Latency: 95th Percentile                     2.585 ms          7.3
> Latency: Maximum                             26.977 ms          7.9
> Average Read Time with Random Writes         1.299 ms          8.1
> Total Run Time 00:00:39.41

HD Tach has been end of lifed. HD Tune appears to be equivalent: http://www.hdtune.com/

For those who might be looking for something capable of testing SQL type scenarios there's Diskspd.exe which has superseded SQLIO.