The average read access time of the 7K400 hasn’t got any worse even though it uses five platters now. The HDS722525VLAT80 wins this test due to its “shortened” platters – its capacity is truncated to 250 billions of bytes for some reason, quite unusually for products from IBM/Hitachi.
But there are differences in the average write access time test. First, my point about the bad compatibility with the Promise Ultra133 TX2 controller is confirmed: the ATA version of the 7K400 is the slowest on this controller, while it performs quite well on the Promise SATA150 TX2. The Serial ATA 7K400 models, however, boast the highest performance. They are accompanied with the senior model of the 7K250 series which has the “shortened platter” advantage.
Next I calculate the ratio between read and write average access times. The result is indicative of the efficiency of sorting of deferred write requests.
The failure of the 7K400 on the Promise Ultra133 TX2 controller is already clear, while the fact that the results of the Serial ATA 7K400 and of the senior 7K250 model coincide means that Hitachi has really developed firmware with new dynamic look-ahead read and deferred write algorithms, but uses them in the flagship models only. The new algorithms should be most effective at processing mixed streams of requests. Let’s check it out right now in the Database pattern.