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.
Obviously for SSDs this is not an issue. We measured read performance at roughly 234MB/sec measured, for this particular test it's the fastest we have ever seen for any storage device (not in RAID).
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, but seek speeds are misleading. Also again, without a physical head that needs moving around, the SSDs are just so fast as they have no mechanical moving parts. Here obviously .. the smaller number is better, 0.1 ms (!).
Here's a little test report of HDTach in both a long READ and WRITE sequence as well. Really fast results, with write performance measured at 187 MB/sec.
SiSoft Sandra HD test
Let's do a synthetic test with Sandra, just to see if we can match the results we've seen in HD Tach.
What SANDRA also does (important for an HDD) is to test at several positions of the HD. See, at the outer part of a platter the performance is slower. The drive index test is what I refer to. The higher the better.
The WD Velociraptor is fast at 99 MB/sec and then the Agility EX shows absolutely brilliant performance up to 241 MB/sec speeds. Sandra returned a write speed of 194 MB/sec matching advertised speeds.
OCZ Agility 3 SSD review OCZ is about to inject an SSD into the market that is labeled Agility 3 SSD. What's the difference in-between Agility 2 and now 3 you might ask ? Well, two primary things really, controller and NAND flash memory type. Labeled with advertised speeds of of 525 MB/sec with write speeds of 500 MB/sec this product should be really interesting for many of you.
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