Database Pattern

Now we return to non-sequential loads. The patterns that emulate the operation of an SQL database at different ratios of writes to reads and at different request queue depths will show us the performance scalability of the HDDs as well as their ability to combine reading with deferred writing.

Let’s first examine the case when there are no write requests at all. Reading only.

The average sector seek time is the most important factor when there is no request queue. The long-out-of-production Deskstar 7K250 is the best HDD in this parameter, as we’ve found above, so it is ahead of the others until a load of 4 outstanding requests when it is overtaken by the two 500GB models with a Serial ATA interface. They seem to make it by means of NCQ. NCQ technology also helps the Deskstar 7K1000 leave last place as the load grows higher. The Deskstar 7K500 shows the best scalability of speed depending on the request queue depth. It had no problems in the threaded tests, either.

When there are write request to be performed, the old Deskstar 7K250 with disabled TCQ is in the lead through most of the load range. The others are roughly equal to each other except for the two 500GB models which are outsiders here. NCQ does not work well for them together with deferred writing whereas the Deskstar 7K1000 seems to have improved in this respect.

When there are no read requests, the damage inflicted on older HDDs by Tagged Command Queuing is obvious. Without this technology every Deskstar fits within ±7% of the average: the T7K500 SATA, 7K500 PATA and 7K400 SATA are the slowest drives here and the newest 7K1000 is close behind the leaders 7K250 and 7K500 SATA.