Now let’s check out diagrams that show a graph with five queue depths for each of the HDDs. This representation is indicative of the efficiency of the drive’s firmware algorithms.
The Hitachi 7K1000 behaves like most other HDDs from this brand. It features effective deferred writing and good NCQ algorithms.
The Samsung is similar to the Hitachi but its NCQ algorithms are somewhat more effective and deferred writing is less aggressive.
Seagate’s early 750GB drives have a very phlegmatic temperament. The desktop 7200.10 and the server-oriented ES have a minimum of deferred writing and request reordering. We should note, however, that the server-oriented version is better at very high loads.
The new generation shows the results of the developer’s work. The new firmware features superb requests reordering. Perhaps Seagate has applied some technologies from Maxtor whose products used to boast excellent NCQ implementation? Anyway, requests reordering and deferred writing are top class in the new firmware. They would be just ideal if it were not for the slump at 30% reads.
Take note that while both models perform requests reordering with the same efficiency, deferred writing is more effective in the desktop 7200.11. The server-oriented Barracuda ES.2 probably doesn’t take too much data into the cache at writing in order to ensure higher reliability: these data are going to be irrecoverably lost in case of a power failure!
And here is another pair of identically behaving drives. Their results are better than those of Seagate’s older models but not by much. Deferred writing has low efficiency, and there is almost no requests reordering.
The older WD7500AYPS already indicated that Western Digital had done a good job on improving the firmware. This model reorders requests better than the above-discussed drives from the same maker. The updated WD7501AYPS has even higher efficiency of requests reordering (it is as efficient as that of Seagate’s new models) and features more efficient deferred writing. Judging by the increased read speed, the drive’s mechanical components have also been improved.