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Disk Response Time and IOMark: Average Positioning Speed

For 10 minutes IOMeter is sending a stream of requests to read and write 512-byte data blocks with a request queue of 1. The total of requests processed by each HDD is much larger than its cache, so we get a sustained response time that doesn’t depend on the HDD’s buffer size.

We’ve got three leaders at reading, all of them from the previous generation: the WD Blue A7, Seagate 7200.11 and WD Black. Among the single-platter products the Samsung F3 is the only one to show a good read response, the rest of them competing with the 5400RPM WD AACS. Take note of the poor response time of the Hitachi 7K1000.C: 18 milliseconds is terribly high for a 7200RPM model. Hopefully, this is caused by some specific problems this HDD has with 512-byte data blocks rather than by too slow heads. Overall, you can see that the transition to 500GB platters has not been easy for any manufacturer. The increased recording density makes it more difficult to position the head over the required track.

The write response time of an HDD depends on how efficiently it can cache incoming requests. There are four leaders: the 7200.11 and 7200.12 series drives from Seagate and the Blue V1 and M9 drives from WD. The Samsung F2 is the only HDD to show a downright poor write response.

Next goes the test of average positioning speed. The drive is being bombarded with read requests like in the response time test, and we calculate the difference between the LBA addresses of the previous and next requests and divide it by the time it took to perform the request. In other words, we have the distance (in gigabytes) the drive’s heads can run through in 1 second.

It is generally hard to predict the result of this test as it depends on lots of factors including the HDD’s recording density, heads and number of platters. We have two leaders here: the Samsung F3 and the Seagate 7200.11. At the bottom of the table we see two power-efficient products (the Seagate LP and the WD Green with 32MB cache) which have fallen behind their opponents from the same category, and the Hitachi 7K1000.C. The latter’s firmware is to blame once again. We just can’t find any other reason for the Hitachi drive’s poor performance.

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