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.
The HD Tach sequential read test is a little bit different from other benchmarks. Most benchmarks create a file on the hard drive and test within that file. The problem is that modern hard drives use a zone bit recording technique that allows different read speeds depending on where the data is located. Data on the outside of the drive is much faster than data recorded on the inside.
SSD itself - no caching enabled (that's seriously fast)
HDtach run 1 - very obvious HDD expected behaviour
HDtach run 2 - You can see cached data kick in
HDtach run 3 - very interesting performance
When we look at write performance we see 109 MB/sec in this test at the first cached run, that's classic HDD performance. Once we reach the 2nd run we are already at 292 MB/sec. The 3rd run shows 291 MB/sec read performance with burst speeds up-to 324 MB/sec.
Write performance could not be tested again as we can not cache an unformatted and partitioned RAW volume.
OCZ Synapse Cache SSD review While OCZ just released the Revodrive Hybrid, they now also launch a seriously fast SSD just for caching. Combined with their Dataplex cache application software and your own HDD, the combination could be just what you are looking for, all at a much better price as well with no limitations to your hardware setup.It's armed with a SandForce 2281 controller and the means to use it, as alongside the SSD you get to use the very same cache software layer the RevoDrive Hybrid uses, Dataplex. A cache in combination with the Synapse SSD offers read speeds of up-to 550MB/s and write performance of up-to 490 MB/sec.