Database Pettern

In the Database pattern the Hard Disk drive has to process random-address read and write requests. The behavior of each HDD at different request queue depths is analyzed below and then a summary of the test is provided at the end.

The Deskstar T7K250 was the first drive Hitachi implemented Native Command Queuing in, and its operation is visible in the graphs at small percentages of writes. The performance growth is low at a small requests queue depth, however. Write requests are obviously processed bypassing the NCQ mechanism.

At a requests queue depth of 64 commands the Serial ATA version of Deskstar T7K250 has no advantages over the ATA version when there are write requests to be processed. It is only when there are no write requests at all and the queue is longer than 8 commands that we can see a difference between them. It means that NCQ won’t be helpful in most of real-life applications. On the contrary, we can expect a reduction of performance considering the dramatic performance hit the HDD suffers when reading multiple data streams in parallel.

The diagrams for the first generation of Serial ATA drives are almost the same except for the efficiency of deferred writing. There are no surprises here. In our Deskstar 7K400 review we noted that this model was slower in the random write test than the same model with an ATA interface. The latter is almost as fast the HDDs of the newer generation here.

The test of writing multiple streams has shown that these four HDDs have similar deferred writing algorithms, so we can’t expect them to differ greatly in write tests.