HD Tach is a physical performance hard drive test for Windows 95/98/ME and Windows NT/2000. In Windows 9X/ME it uses a special kernel mode VXD to get maximum accuracy by bypassing the file system. A similar mechanism is used in Windows NT/2000/XP. HD Tach reads from areas all over the hard drive and reports an average speed. It also logs the read speeds to a text file that you can load into a spreadsheet and graph to visually read the results of the test.

Hard Drive Tach 3.0.1.0 - Benchmark Results
	Physical Drive Size	Access Time	Read Burst Speed	Read Speed Max	Read Speed Min	Read speed Avg	CPU utilization
Western Digital Raptor WD740 (single)	74GB	13.8ms	121.7	72	53	65.1	4%
Western Digital Raptor WD740 (RAID 0)	140GB	7.8ms	212.1	145	105	126.5	4%
Western Digital Raptor WD740 (RAID 1)	74GB	7.8ms	121.6	72	52	65.1	4%
Seagate Barracuda ST380013AS (single)	80GB	12.8	91.1	59	31	47.2	2%
Seagate Barracuda ST380013AS (RAID0)	160GB	12.5	112.1	110	61	84.9	4%
Seagate Barracuda ST380013AS (RAID1)	80GB	12.7	91.5	58	31	47.2	4%
Units:		ms	MB/s	MB/s	MB/s	MB/s	%

Transfer Graph: Single Raptor WD740

Transfer Graph: Dual Raptor WD740 RAID 0 Stripe

Transfer Graph: Dual Raptor WD740 RAID 1 Mirror

Like Sandra, HDTach does not see a performance difference between lone and Mirrored RAID 1 drive configuration. The lone WD740 Raptor averages a 65.1MB/s sustained data read, which is great. This benchmark is overly kind to striped RAID 0 sets as opposed to single drives, so I would not expect to see a real-life 50% performance advantage from striping. Still the numbers for the Western Digital drives continue to be impressive.