SSD Performance HD Tach

HD Tach

HD Tach is a physical performance hard drive test that uses a special kernel mode VXD to get maximum accuracy by bypassing the file system.

We look at average (not peak!) write performance in this test. In addition to sequential read performance, HD Tach tests the drive's random access time. Random access is the true measure of seek speed. Many drives advertise sub 10 millisecond seek speeds.

Above: the Samsung 850 EVO mSATA 1TB

Above: the Samsung 850 EVO M.2 120GB - The write dip is due to the small 120GB volume size, the SSD can only write to 2 ICs simultaniously opposed to 4, thus it lacks memory channels.
The 250GB and higher versions will not show this behaviour.

Also again, without a physical head that moves around, the SSDs are just so fast as they have no mechanical moving parts. Here obviously, the smaller the number is, the better. In this case, 0.1 ms.