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With this difference in platter density, the equal read speed means that the HDD with the higher platter density has a lower rotation speed. And I can measure it.

This is a screenshot of the IOMark report on the disk cache and the spindle speed. Underlined is the real spindle rotation speed of the Caviar GP.

Whatever the press releases say, the platters of this HDD rotate at a speed of 5400rpm. So, I have found one part of the secret of this economical drive. It spends less power to maintain the rotation speed.

Why did Western Digital choose this rotation speed for the GP disk? Is it because of power saving reasons? I guess not. If Western Digital had had the technical opportunity to release a 1-terabyte drive with a spindle rotation speed of 7200rpm, it would have done it. And the company did not because it didn’t have the opportunity. But all the competitors releasing 1-terabyte drives, Western Digital couldn’t help introducing its own model, trying to present its low speed as an advantage.

Next I will check out the speed at which the HDDs can communicate with their cache buffer. I will use IOMark again. IOMeter can benchmark the speed of reading from and writing into the buffer and can show the correlation between the speed and the size of the requested data block.

I should note that if I began to test the HDDs as they were right out of the boxes, the drives from Seagate and Hitachi would have been not as good as their opponents. The fact is these HDDs come with an interface bandwidth limitation. They have SATA-300 electronics but their interface speed is limited to 1.5GBps by default, i.e. to the speed of SATA-150. Why? To ensure better compatibility with old SATA controllers (integrated into mainboards or external cards). It is easy to remove this limitation on the Seagate drives: you just have to remove a jumper at the butt-end of the drive where the interface and power connectors are located. There is only one jumper there, so you can’t make a mistake. It is somewhat more difficult with Hitachi’s HDDs – you have to use the Hitachi Feature Tool for that. This is a very powerful tool, by the way. Changing the interface speed is not the only thing you can do with it.

So, in this section I will show you the results of the HDDs from Hitachi and Seagate with the interface speed limitation enabled and disabled. In the next sections the HDDs will be tested in SATA-300 mode. The pairs of disks from Hitachi and Seagate (Deskstar-Ultrastar and Barracuda 7200.11-Barracuda ES.2) have identical results, so I’ll publish the diagrams for one HDD from each pair.

The Hitachi comes first:

Hitachi Deskstar 7K1000 @ SATA150

You can see the HDD quickly reaching the interface bandwidth limit. It should do better in SATA-300 mode. There is but a small difference between the speed of reading from and writing into the cache.

Hitachi Deskstar 7K1000 @ SATA300

When in SATA-300 mode, the speed grows faster on small data blocks. The maximums of speed fall on data block sizes that are multiples of 256 (128KB).

Samsung Spinpoint F1

The Samsung drew a very nice-looking graph and surpassed the Hitachi in both burst read and burst write speeds.

Seagate Barracuda 7200.11 @SATA150

The Seagate stumbles on data blocks larger than 256 sectors. The burst write graph shows this most clear.

Seagate Barracuda 7200.11 @SATA300

With the interface bandwidth limitation removed, the Seagate pushes the burst read bar even higher, outperforming the Samsung. However, the Seagate’s dislike of large-size data blocks seems to be unrelated to the interface bandwidth.

WD Caviar GP

The HDD from Western Digital has the lowest speed of working with the cache among the tested HDDs but it is also free from problems with large data blocks (it is a problem when the burst speed is lower than the HDD’s linear speed).

So, there are two winners in this test. The Seagate boasts the highest data-transfer speed while the Samsung is fast and also indifferent to the data block size.

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