Winding up this part of our tests, we will build diagrams showing the performance of each HDD at five different request queue depths.
The Hitachi drives all behave in the same manner. They have good deferred writing algorithms but their read request reordering is weak and only shows up at long queue depths.
The Samsung drives can do some deferred writing and increase their performance somewhat at higher request queue depths, but that’s about all the good news about them. These HDDs find it very hard to work under mixed loads, especially at high queue depths. They just don’t know what performance optimization algorithms to apply then.
The Seagate series of 5400RPM drives is very consistent. The firmware of the 500GB drive has been inherited by the 640GB model except that the deferred writing algorithms have become less effective at high request queue depths. The performance growth at reading can still be observed.
The Seagate 7200.4 is quite good at reading, but its weak deferred writing algorithms make it much slower than the other HDDs from Seagate at high percentages of writes.
The old WD BEVT drives behave similar to their desktop counterparts and deliver effective deferred writing and good request reordering. They also have a characteristic performance hit at 90% writes and long request queue depths. The new models with Advanced Format behave in the same manner except that their deferred writing is not that effective.