Winding up this section of our tests we will show you a diagram with each drive’s performance at five different queue depths.
Aren’t these graphs odd? Yes, we’ve got used to see quite a different picture with 7200rpm HDDs. The reason is that SAS drives do not have aggressive deferred writing algorithms (being reliability-optimized, SAS drives prefer not to store too much data in the deferred writing cache) but have a high reading performance due to low response time.
While the two junior models of the Fujitsu MBA3 RC series don’t differ much from their predecessors, the 300GB model shows a completely different behavior. The HDD does not change performance when the queue depth is increased from 4 to 16 requests. The further performance growth is very modest. So, this HDD obviously has different firmware.
Hitachi’s second and third generations of SAS drives behave in the same way and differ strikingly from the 15K147. Frankly speaking, we like the newer version more. Notwithstanding its less predictable performance and lower speed at very long queue depths, it is overall superior to its predecessor as it delivers higher performance at 50% and higher writes when the queue is shorter.