Defragmentation with NCQ

Next we tested each HDD once again, this time with enabled NCQ, i.e. with AHCI support enabled in the mainboard’s BIOS.

The overall picture didn’t change much except for the dash of the Samsung drive which managed to overtake WD’s 10,000rpm models due to enabled NCQ.

The following diagram combines the results of the HDDs in the two tests so that we could easily see which HDD profited (or lost) most from enabled NCQ.

This diagram looks discouraging.

NCQ doesn’t improve the HDDs?performance much. Moreover, most of our HDDs performed worse when NCQ was enabled than otherwise. Those few HDDs that profited somehow from this technology include the Hitachi HDT725050VLA360, Samsung HD501LJ and?the WD740GD for which NCQ support is not declared! The rest of the HDDs are slower by 10-30 seconds compared with their own results with disabled NCQ. This is very odd because this technology should have showed its best under such conditions, when data is copied within the same disk.

Perhaps the defragmenter we use does not generate disk requests that can be enqueued? On the other hand, this defragmenter is the most popular one because an overwhelming majority of users prefer Windows?integrated tools to third-party alternatives.