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Low-Level Characteristics

First, I’m going to check the Deskstar 7K400 with our new tools from the IOMark suite.

For me, it was a kind of revelation that the Serial ATA and Parallel ATA versions of the Deskstar 7K400 use firmware with different look-ahead reading! That is, they didn’t equip the HDS724040KLAT80 with the adaptive algorithms we could see in all Deskstar 7K250 models with an 8MB buffer (see our article called Hitachi Deskstar 7K250: Vancouver 3 HDD Review). This drive just got classic look-ahead reading that traces its origin back to the Vancouver2, but somewhat less aggressive and segmented. We’ll see in the following tests how bad this is. Right now let’s analyze the rest of the data.

The segmentation of the Deskstar 7K400 is somewhat smaller than that of the previous models. As you know from our Vancouver3 review, Hitachi drew a separating line between senior and junior models by means of segmentation, but this separation was rather vague in some cases. Thus, there can be situations with the 7K400 losing due to the lesser flexibility of the look-ahead algorithms, but the probability of this is very small. By the way, Hitachi still declares up to 128 buffer segments at reading, but we still don’t see that in reality.

Despite the smaller total volume of the buffer (more memory is allotted for the firmware), the read buffer size of the 7K400 has become more than 100 kilobytes bigger. But it seems like only the Serial ATA models, with adaptive look-ahead reading, are going to profit by that. Another consequence of the growth of the read buffer may be a reduction of the deferred write buffer. I can’t yet check this out, but I will keep this possibility in mind when analyzing the results of the tests that depend on deferred writing.

The average access time (the AAT column of the table) has worsened by a negligible fraction of millisecond against the previous models. Moreover, the average seek time (the AST column) fully conforms to what the manufacturer promised.

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